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Acute feeding with almonds compared to a carbohydrate-based snack improves appetite-regulating hormones with no effect on self-reported appetite sensations: a randomised controlled trial.
Carter, S, Hill, AM, Buckley, JD, Tan, SY, Rogers, GB, Coates, AM
European journal of nutrition. 2023;62(2):857-866
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Long-term regulation of body weight is controlled by balancing energy intake with energy expenditure. Understanding the role of specific food items and their impact on energy intake may assist in promoting weight reduction and weight loss maintenance for people with obesity. The aim of this study was to compare the effects of eating almonds or a carbohydrate-based snack on appetite-regulating hormones, self-reported appetite ratings, and short-term energy intake. This study is based on data obtained from a parallel arm randomised controlled trial. Participants were males and females, aged between 25 and 65 years who were randomly assigned to either the almond or the snack bar treatment groups based on age, sex and body mass index. Results show that the consumption of almonds resulted in a smaller C-peptide response and a larger glucose-dependent insulinotropic polypeptide [pancreatic hormone], glucagon-like peptide 1 [peptide hormone] (timepoint comparisons only), glucagon and pancreatic polypeptide response compared to consuming an isocaloric carbohydrate-rich snack bar. Furthermore, although not significant, the almond group consumed 300 kJ less energy in the meal challenge, 270 kJ of which came from discretionary foods, which may be a clinically important benefit in weight management. Authors conclude that foods that promote satiety help to regulate energy balance and may assist with weight management. However, future studies should consider testing food dose and composition carefully as the volume of food, its sensory qualities, and the acceptance of the food respective of usual meal patterns, may be important in eliciting a feeling of fullness and satisfaction.
Abstract
PURPOSE Early satiety has been identified as one of the mechanisms that may explain the beneficial effects of nuts for reducing obesity. This study compared postprandial changes in appetite-regulating hormones and self-reported appetite ratings after consuming almonds (AL, 15% of energy requirement) or an isocaloric carbohydrate-rich snack bar (SB). METHODS This is a sub-analysis of baseline assessments of a larger parallel-arm randomised controlled trial in overweight and obese (Body Mass Index 27.5-34.9 kg/m2) adults (25-65 years). After an overnight fast, 140 participants consumed a randomly allocated snack (AL [n = 68] or SB [n = 72]). Appetite-regulating hormones and self-reported appetite sensations, measured using visual analogue scales, were assessed immediately before snack food consumption, and at 30, 60, 90 and 120 min following snack consumption. A sub-set of participants (AL, n = 49; SB, n = 48) then consumed a meal challenge buffet ad libitum to assess subsequent energy intake. An additional appetite rating assessment was administered post buffet at 150 min. RESULTS Postprandial C-peptide area under the curve (AUC) response was 47% smaller with AL compared to SB (p < 0.001). Glucose-dependent insulinotropic polypeptide, glucagon and pancreatic polypeptide AUC responses were larger with AL compared to SB (18%, p = 0.005; 39% p < 0.001; 45% p < 0.001 respectively). Cholecystokinin, ghrelin, glucagon-like peptide-1, leptin and polypeptide YY AUCs were not different between groups. Self-reported appetite ratings and energy intake following the buffet did not differ between groups. CONCLUSION More favourable appetite-regulating hormone responses to AL did not translate into better self-reported appetite or reduced short-term energy consumption. Future studies should investigate implications for longer term appetite regulation. ANZCTR REFERENCE NUMBER ACTRN12618001861246 2018.
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Evidence of lifestyle interventions in a pregnant population with chronic hypertension and/or pre-existing diabetes: A systematic review and narrative synthesis.
Goddard, L, Patel, R, Astbury, NM, Tucker, K, McManus, RJ
Pregnancy hypertension. 2023;31:60-72
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Chronic hypertension complicates ≤5 % of pregnancies, and those entering pregnancy with a pre-existing diagnosis of diabetes has a global prevalence of between 0.5 % and 2.6 %. The aim of this study was to collate the evidence around lifestyle interventions during pregnancy for women with chronic hypertension and/or pre-existing diabetes (type 1 and type 2). This study is a systematic review and meta-analysis of nine randomised controlled trials. Results show lack of clarity and data on the effect of lifestyle interventions in pregnant women with chronic hypertension and/or pre-existing diabetes, thereby exposing key gaps in the literature. Authors conclude that there is a shortage of primary interventional studies examining the effect of lifestyle interventions in high-risk pregnant populations who enter pregnancy with chronic conditions.
Abstract
BACKGROUND Pregnant people with chronic hypertension, pre-existing diabetes or both are at high risk of developing cardiovascular disease. Lifestyle interventions play an important role in disease management in non-pregnant populations. AIM: To review the existing evidence of randomised controlled trials (RCTs) that examine lifestyle interventions in pregnant people with chronic hypertension and/or pre-existing diabetes. METHODS A systematic review and narrative synthesis was conducted. Five electronic databases were searched from inception to April 2021 for RCTs evaluating antenatal lifestyle interventions in people with chronic hypertension and/or pre-existing diabetes with outcomes to include weight or blood pressure change. RESULTS Nine randomised controlled trials including 7438 pregnant women were eligible. Eight studies were mixed pregnant populations that included women with chronic hypertension and/or pre-existing diabetes. One study included only pregnant women with pre-existing diabetes. Intervention characteristics and procedures varied and targeted diet, physical activity and/or gestational weight. All studies reported weight and one study reported blood pressure change. Outcome data were frequently unavailable for the subset of women of interest, including subgroup data on important pregnancy and birth complications. Eligibility criteria were often ambiguous and baseline data on chronic hypertension was often omitted. CONCLUSION A lack of primary interventional trials examining the effect of lifestyle interventions on weight and blood pressure outcomes in pregnant populations with chronic hypertension and/or pre-existing diabetes was evident. Lifestyle modification has the potential to alter disease progression. Future trials should address the ambiguity and frequent exclusion of these important populations.
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Effects of a Dulaglutide plus Calorie-Restricted Diet versus a Calorie-Restricted Diet on Visceral Fat and Metabolic Profiles in Women with Polycystic Ovary Syndrome: A Randomized Controlled Trial.
Zhang, Y, Qu, Z, Lu, T, Shao, X, Cai, M, Dilimulati, D, Gao, X, Mao, W, Hu, F, Su, L, et al
Nutrients. 2023;15(3)
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Polycystic ovary syndrome (PCOS) is a unification of reproductive endocrine and metabolic disorders. Lifestyle and weight management, particularly dietary intake aimed at weight loss, are initial treatment strategies for PCOS. A calorie-restricted diet (CRD) seems to be the optimal dietary pattern for weight management in the PCOS population. The aim of this study was to evaluate modifications in fat distribution, the androgenic state, and metabolic profiles in the overweight and obese PCOS-affected population, who obtained modest and equivalent weight loss induced by a CRD regimen with or without Dulaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist (RA). This study was a randomised controlled trial which enrolled 68 females diagnosed with PCOS. Participants were randomly assigned to receive to one of the two groups: a GLP-1 RA combined with CRD or CRD alone. Results showed that participants in the GLP-1 RA + CRD group took a shorter time to achieve a 7% weight loss goal than those in the CRD group. Furthermore, both interventions had similar positive effects in improving menstrual frequency and reducing levels of blood pressure, insulin, aminotransferases, lipids, total fat mass, total lean mass, and abdominal subcutaneous adipose tissue mass after equivalent weight loss. Authors conclude that their findings support the importance of dietary intervention as a first-line treatment in women with PCOS, and that GLP-1 RA therapy offers an effective and generally tolerable adjunct therapy to aid in achieving weight targets based on dietary therapy in overweight and obese women with PCOS.
Abstract
The effects of dulaglutide and a calorie-restricted diet (CRD) on visceral adipose tissue (VAT) and metabolic profiles in polycystic ovary syndrome (PCOS) have not been extensively investigated. In this study, we investigated whether dulaglutide combined with CRD could further reduce VAT and promote clinical benefits as compared with a CRD regimen alone in overweight or obese PCOS-affected women. Between May 2021 and May 2022, this single-center, randomized, controlled, open-label clinical trial was conducted. Overall, 243 participants with PCOS were screened, of which 68 overweight or obese individuals were randomly randomized to undergo dulaglutide combined with CRD treatment (n = 35) or CRD treatment alone (n = 33). The duration of intervention was set as the time taken to achieve a 7% weight loss goal from baseline body weight, which was restricted to 6 months. The primary endpoint was the difference in the change in VAT area reduction between the groups. The secondary endpoints contained changes in menstrual frequency, metabolic profiles, hormonal parameters, liver fat, and body composition. As compared with the CRD group, the dulaglutide + CRD group had a considerably shorter median time to achieve 7% weight loss. There was no significant between-group difference in area change of VAT reduction (-0.97 cm2, 95% confidence interval from -14.36 to 12.42, p = 0.884). As compared with CRD alone, dulaglutide + CRD had significant advantages in reducing glycated hemoglobin A1c and postprandial plasma glucose levels. The results of the analyses showed different changes in menstruation frequency, additional metabolic profiles, hormonal markers, liver fat, and body composition between the two groups did not differ significantly. Nausea, vomiting, constipation, and loss of appetite were the main adverse events of dulaglutide. These results emphasize the value of dietary intervention as the first line of treatment for PCOS-affected women, while glucagon-like peptide 1 receptor agonist therapy provides an efficient and typically well tolerated adjuvant therapy to aid in reaching weight targets based on dietary therapy in the population of overweight/obese PCOS-affected women.
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Is Extra Virgin Olive Oil the Critical Ingredient Driving the Health Benefits of a Mediterranean Diet? A Narrative Review.
Flynn, MM, Tierney, A, Itsiopoulos, C
Nutrients. 2023;15(13)
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Cardiovascular diseases (CVDs) are the largest contributor to deaths globally, followed by cancers, chronic respiratory diseases and diabetes. It is estimated that 90% of deaths from CVD can be prevented with modifiable risk factors such as diet. The Mediterranean diet, which is rich in extra virgin olive oil (EVOO), is important in the prevention of chronic diseases. There is however very little focus on differentiating healthy fats such as EVOO from other fats and oils in dietary guidelines. This review of 34 studies aims to compare the effect of diets that include EVOO on cardiometabolic risk factors for heart disease, metabolic syndrome, and type 2 diabetes. It looks at the effects on blood pressure (SBP), low- and high-density lipoprotein cholesterol, (HDP-c and LDD-c) fasting blood glucose (FBG) and body weight. It also assesses from published studies the minimum daily amount of EVOO and the shortest time needed to see improvements in the risk factors. There is evidence to support EVOO in improving SBP in patients with high blood pressure, with studies suggesting that specific phenols in the oil may be important compared with a refined olive oil. Compared with other dietary fats or low-fat diets, EVOO can decrease LDL-c and increase HDL-c. Diets including daily EVOO are effective for weight loss. The effect of EVOO on FBG compared with other diets is not yet clear. The authors state that EVOO would be a far superior choice compared with other dietary fats, low-fat diets, or refined olive oil. The daily use of EVOO starting at approximately two tablespoons a day will improve a range of risk factors in as few as three weeks.
Abstract
Most chronic diseases are preventable with a healthy diet, although there is debate about the optimal dietary approach. Increasingly more countries are focusing on food-based guidelines rather than the traditional nutrient-based approach. Although there is good agreement on plant foods, controversy remains about the types and amounts of fats and oils. This narrative review aims to systematically summarize and evaluate the latest evidence on the protective effects of extra virgin olive oil (EVOO) on disease risk factors. A systematic search of the relevant literature using PubMed, Cochrane Library, and Embase databases was conducted for the years 2000 through December 2022. A narrative synthesis was then undertaken. Of 281 retrieved articles, 34 articles fulfilled our inclusion criteria and were included. Compared with other dietary fats and low-fat diets, EVOO is superior in the management of clinical biomarkers including lowering blood pressure and LDL-c, increasing protective HDL-c, improving glycemic control, and weight management. The protective effects of EVOO are likely due to its polyphenol content rather than the monounsaturated fat content. It is therefore important to promote the regular use of EVOO in the context of healthy dietary patterns such as the Mediterranean diet for maximal health benefit.
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Dietary carbohydrate restriction augments weight loss-induced improvements in glycaemic control and liver fat in individuals with type 2 diabetes: a randomised controlled trial.
Thomsen, MN, Skytte, MJ, Samkani, A, Carl, MH, Weber, P, Astrup, A, Chabanova, E, Fenger, M, Frystyk, J, Hartmann, B, et al
Diabetologia. 2022;65(3):506-517
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The carbohydrate restricted diet has been shown to be beneficial for Type 2 diabetes (T2D) management and reducing cardiovascular disease risk. This open-label, parallel randomised controlled trial involved Type 2 diabetic patients taking antidiabetic medications who restricted their energy intake by following either a carbohydrate-reduced high protein diet or a conventional diabetic diet. Participants in both groups had a 5.9% reduction in body weight, similar changes in fasting NEFA, apoB, apoA-1, total cholesterol, LDL-cholesterol, HDL-cholesterol, and non-HDL cholesterol, and a significant reduction in fasting glucose, insulin, C-peptide, and HOMA2-IR after 6 weeks of intervention. Carbohydrate-reduced high protein diet group showed a greater reduction in HbA1c and diurnal mean glucose, glycaemic variability, fasting triacylglycerol concentration and liver fat content. Carbohydrate-reduced high protein diet caused an adverse reaction in some patients, and those following a carbohydrate-reduced high protein diet excreted more urea than those eating a conventional diabetic diet. To confirm the results of this study, long-term robust studies are needed. This study can assist healthcare professionals in understanding the benefits of following a carbohydrate-reduced high protein diet in improving glycaemic control, triglyceride levels, and reducing body weight in Type 2 diabetes patients.
Abstract
AIMS/HYPOTHESIS Lifestyle modification and weight loss are cornerstones of type 2 diabetes management. However, carbohydrate restriction may have weight-independent beneficial effects on glycaemic control. This has been difficult to demonstrate because low-carbohydrate diets readily decrease body weight. We hypothesised that carbohydrate restriction enhances the beneficial metabolic effects of weight loss in type 2 diabetes. METHODS This open-label, parallel RCT included adults with type 2 diabetes, HbA1c 48-97 mmol/mol (6.5-11%), BMI >25 kg/m2, eGFR >30 ml min-1 [1.73 m]-2 and glucose-lowering therapy restricted to metformin or dipeptidyl peptidase-4 inhibitors. Participants were randomised by a third party and assigned to 6 weeks of energy restriction (all foods were provided) aiming at ~6% weight loss with either a carbohydrate-reduced high-protein diet (CRHP, percentage of total energy intake [E%]: CH30/P30/F40) or a conventional diabetes diet (CD, E%: CH50/P17/F33). Fasting blood samples, continuous glucose monitoring and magnetic resonance spectroscopy were used to assess glycaemic control, lipid metabolism and intrahepatic fat. Change in HbA1c was the primary outcome; changes in circulating and intrahepatic triacylglycerol were secondary outcomes. Data were collected at Copenhagen University Hospital (Bispebjerg and Herlev). RESULTS Seventy-two adults (CD 36, CRHP 36, all white, 38 male sex) with type 2 diabetes (mean duration 8 years, mean HbA1c 57 mmol/mol [7.4%]) and mean BMI of 33 kg/m2 were enrolled, of which 67 (CD 33, CRHP 34) completed the study. Body weight decreased by 5.8 kg (5.9%) in both groups after 6 weeks. Compared with the CD diet, the CRHP diet further reduced HbA1c (mean [95% CI] -1.9 [-3.5, -0.3] mmol/mol [-0.18 (-0.32, -0.03)%], p = 0.018) and diurnal mean glucose (mean [95% CI] -0.8 [-1.2, -0.4] mmol/l, p < 0.001), stabilised glucose excursions by reducing glucose CV (mean [95% CI] -4.1 [-5.9, -2.2]%, p < 0.001), and augmented the reductions in fasting triacylglycerol concentration (by mean [95% CI] -18 [-29, -6]%, p < 0.01) and liver fat content (by mean [95% CI] -26 [-45, 0]%, p = 0.051). However, pancreatic fat content was decreased to a lesser extent by the CRHP than the CD diet (mean [95% CI] 33 [7, 65]%, p = 0.010). Fasting glucose, insulin, HOMA2-IR and cholesterol concentrations (total, LDL and HDL) were reduced significantly and similarly by both diets. CONCLUSIONS/INTERPRETATION Moderate carbohydrate restriction for 6 weeks modestly improved glycaemic control, and decreased circulating and intrahepatic triacylglycerol levels beyond the effects of weight loss itself compared with a CD diet in individuals with type 2 diabetes. Concurrent differences in protein and fat intakes, and the quality of dietary macronutrients, may have contributed to these results and should be explored in future studies. TRIAL REGISTRATION ClinicalTrials.gov NCT03814694. FUNDING The study was funded by Arla Foods amba, The Danish Dairy Research Foundation, and Copenhagen University Hospital Bispebjerg Frederiksberg.
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The effect of periodic ketogenic diet on newly diagnosed overweight or obese patients with type 2 diabetes.
Li, S, Lin, G, Chen, J, Chen, Z, Xu, F, Zhu, F, Zhang, J, Yuan, S
BMC endocrine disorders. 2022;22(1):34
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Currently, the ketogenic diet is gaining popularity in managing Type 2 diabetes (T2D). Ketogenic diets replace carbohydrates with fat and include limited carbohydrates and adequate protein. This randomised controlled trial evaluated the effects of the 12-week ketogenic diet on sixty overweight or obese T2D patients. Both the ketogenic and control diabetes diet groups achieved significant reductions in weight, body mass index, waist circumference, triglycerides, total cholesterol, low-density lipoprotein, high-density lipoprotein, fasting blood glucose, fasting insulin, and HbA1c. However, the ketogenic group showed significantly greater reductions in body mass, blood lipids, and blood glucose than the control group. In the ketogenic diet group, serum uric acid levels were higher than those in the control diet group. It was found that the control diet group adhered to the diet for a longer period than the ketogenic diet group, whose willingness to adhere to the diet long-term was weaker. More robust long-term studies are needed to evaluate the long-term effects of a ketogenic diet. In this study, more patients who followed the ketogenic diet experienced hypoglycaemic events during the first four weeks. Healthcare providers should exercise caution when recommending a short term therapeutic ketogenic diet.
Abstract
BACKGROUND The ketogenic diet (KD) is characterized by fat as a substitute of carbohydrates for the primary energy source. There is a large number of overweight or obese people with type 2 diabetes mellitus (T2DM), while this study aims to observe periodic ketogenic diet for effect on overweight or obese patients newly diagnosed as T2DM. METHODS A total of 60 overweight or obese patients newly diagnosed as T2DM were randomized into two groups: KD group, which was given ketogenic diet, and control group, which was given routine diet for diabetes, 30 cases in each group. Both dietary patterns lasted 12 weeks, and during the period, the blood glucose, blood lipid, body weight, insulin, and uric acid before and after intervention, as well as the significance for relevant changes, were observed. RESULTS For both groups, the weight, BMI(body mass index), Waist, TG (triglyceride), TC(cholesterol), LDL (low-density lipoprotein cholesterol), HDL (high-density lipoprotein cholesterol), FBG (fasting glucose), FINS (fasting insulin), HbA1c (glycosylated hemoglobin) were decreased after intervention (P < 0.05), while the decrease rates in the KD group was more significant than the control group. However, UA(serum uric acid) in the KD group showed an upward trend, while in the control group was not changed significantly (P > 0.05).The willingness to adhere to the ketogenic diet over the long term was weaker than to the routine diet for diabetes. CONCLUSION Among the overweight or obese patients newly diagnosed as type 2 diabetes mellitus, periodic ketogenic diet can not only control the body weight, but also control blood glucose and lipid, but long-term persistence is difficult.
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Efficacy and safety of oral alpha-lipoic acid supplementation for type 2 diabetes management: a systematic review and dose-response meta-analysis of randomized trials.
Jibril, AT, Jayedi, A, Shab-Bidar, S
Endocrine connections. 2022;11(10)
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Many studies have shown that type 2 diabetes is associated with increased formation of free radicals and decreased antioxidant potential, leading to oxidative damage of cell components. Increased formation of free radicals and decreased antioxidant potential, coupled with lipid abnormalities, are substantial risk factors for developing complications, especially microvascular ones. The aim of this study was to investigate the effect of oral supplementation of alpha-lipoic acid (ALA) on cardiometabolic risk factors in patients with type 2 diabetes. This study is a systematic review and dose–response meta-analysis of 16 randomised controlled trials with a total of 1035 patients with type 2 diabetes. Results show that: - each 500 mg/day oral ALA supplementation reduced haemoglobin A1c and body weight but did not affect low-density lipoprotein cholesterol concentration. - ALA supplementation reduced c-reactive protein, fasting plasma glucose, serum triglycerides, and diastolic blood pressure but it had no affect on serum total cholesterol and high-density lipoprotein cholesterol concentrations and systolic blood pressure. Authors conclude that their findings do not support ALA supplementation in clinical practice for patients with type 2 diabetes.
Abstract
OBJECTIVE To examine the dose-dependent influence of oral alpha-lipoic acid (ALA) supplementation on cardiometabolic risk factors in patients with type 2 diabetes (T2D). DESIGN We followed the instructions outlined in the Cochrane Handbook for Systematic Reviews of Interventions and the Grading of Recommendations, Assessment, Development, and Evaluation Handbook to conduct our systematic review. The protocol of the study was registered in PROSPERO (CRD42021260587). METHOD We searched PubMed, Scopus, and Web of Science to May 2021 for trials of oral ALA supplementation in adults with T2D. The primary outcomes were HbA1c, weight loss, and LDL cholesterol (LDL-C). Secondary outcomes included fasting plasma glucose (FPG), triglyceride (TG), C-reactive protein (CRP), and blood pressure. We conducted a random-effects dose-response meta-analysis to calculate the mean difference (MD) and 95% CI for each 500 mg/day oral ALA supplementation. We performed a nonlinear dose-response meta-analysis using a restricted cubic spline. RESULTS We included 16 trials with 1035 patients. Each 500 mg/day increase in oral ALA supplementation significantly reduced HbA1c, body weight, CRP, FPG, and TG. Dose-response meta-analyses indicated a linear decrement in body weight at ALA supplementation of more than 600 mg/day (MD600 mg/day: -0.30 kg, 95% CI: -0.04, -0.57). A relatively J-shaped effect was seen for HbA1c (MD: -0.32%, 95% CI: -0.45, -0.18). Levels of FPG and LDL-C decreased up to 600 mg/day ALA intake. The point estimates were below minimal clinically important difference thresholds for all outcomes. CONCLUSION Despite significant improvements, the effects of oral ALA supplementation on cardiometabolic risk factors in patients with T2D were not clinically important.
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Low-carbohydrate diets and men's cortisol and testosterone: Systematic review and meta-analysis.
Whittaker, J, Harris, M
Nutrition and health. 2022;28(4):543-554
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Testosterone is the primary male sex hormone, and vital for reproductive development and function. Moreover, low endogenous testosterone is associated with an increased risk of chronic disease, including type 2 diabetes and cardiovascular disease. The aim of this study was to investigate the effects of low- versus high-carbohydrate diets on mens' testosterone and cortisol. This study is a systematic review and meta-analysis of twenty-seven studies with a total of 309 participants. Twelve of these studies were randomised trials whilst the rest were non-randomised. Results show an increase in resting and post-exercise cortisol on short-term low-carbohydrate diets (<3 weeks). In fact, resting cortisol levels return to baseline after <3 weeks on a LC diet, whilst post-exercise cortisol remains elevated. Furthermore, high-protein diets cause a large decrease in resting total testosterone. Authors conclude that further research is required in order to warrant their findings.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Short-term LC-diets diets cause a moderate increase in resting and post-exercise cortisol however this effect is not seen in LC-diets followed for great than 3 weeks
- HP-LC diets caused a statistically significant decrease in resting TT, suggesting caution in relation to endocrine effects of LC diets
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction:
A systematic review and network meta-analysis was conducted on the effects of low-carbohydrate (LC) versus high-carbohydrate (HC) diets on men’s testosterone and cortisol.
The review was registered with PROSPERO and reported using PRISMA 2020 checklists.
Methods:
A comprehensive search strategy was used to find intervention studies looking at healthy adult males and LC diets of <35% carbohydrate. Studies were assessed for quality using the Cochrane Risk of Bias tool. Sub-group analyses was conducted for diet duration, protein intake and exercise duration.
Results:
The literature search resulted in 27 studies with a total of 309 healthy adult male participants, age: 27.3 ± 4.7 (to minimise variation in steroid hormone metabolism), body mass: 78.6± 7.1kg and BMI: 24.8 ±1.6. 12 randomised and 15 non-randomised controlled trials were analysed. 21 studies were considered low risk bias, 5 medium and 1 high risk.
- Short-term (<3 weeks) LC diets moderately increased resting cortisol (0.41 [0.16, 0.66], p < 0.01) when compared to HC diets.
- Long-term (≥3 weeks) LC diets had no consistent effect on resting cortisol
- LC diets resulted in higher post-exercise cortisol, after long-duration exercise (≥20 min): 0 h (0.78 [0.47, 1.1], p < 0.01), 1 h (0.81 [0.31, 1.31], p < 0.01), and 2 h (0.82 [0.33, 1.3], p < 0.01).
- The overall results for resting total testosterone (TT) showed a significant decrease on LC versus HC diets (SMD = −0.48, p = 0.01. However, subgroup analyses revealed this effect to be limited to high-protein (HP) LC diets, which yielded a very large decrease in TT (SMD = −1.08, p < 0.01; ∼5.23 nmol/L), albeit in a small sample (n = 26).
- Moderate protein (MP) (<35%), low-carbohydrate diets had no consistent effect on resting total testosterone, however high-protein (≥35%), low-carbohydrate diets greatly decreased resting (−1.08 [−1.67, −0.48], p < 0.01) and post-exercise total testosterone (−1.01 [−2, −0.01] p = 0.05).
- There was no overall effect of LC versus HC diets on 0 h post-exercise TT (SMD = −0.03, p = 0.95). However, subgroup analysis showed 0 h post-exercise was non-significantly higher on long-term LC versus HC diets (SMD = 0.44, p = 0.18), and much lower on short-term LC versus HC diets (SMD = −1.01, p = 0.05)
Conclusion:
This systematic review and metanalysis found an increase in resting and post-exercise cortisol on short-term LC diets. Cortisol does return to baseline in the first 3 weeks of a low-carbohydrate (LC) diet. The same response is, however, not seen in post-exercise cortisol, which remains elevated. In addition, the review showed that compared to moderate-protein diets, HP diets were found to cause a large decrease in resting and post-exercise TT (∼5.23 nmol/L).
Clinical practice applications:
The results of this review suggest that exercising whilst following a LC diet can increase cortisol in the short term, but not long-term. This suggests a period of diet adaptation. The effects of long-term LC diets on cardiovascular disease risk is uncertain and healthcare practitioners should monitor client responses and keep up-to-date with new research in this area
Since HP-LC diets were found to significantly decrease resting testosterone it highlights the need to ensure that protein intake does not exceed the urea cycle’s capacity due to potential adverse endocrine effects.
For clients where there is a desire to increase strength, power and hypertrophy, a MP-LC diet could be of benefit, as it showed potential to signal an increased anabolic state post exercise..
NB: Since the review only included a low number of studies and saw within these some heterogeneity that could not be explained, more research is needed before the paper’s findings can be conclusive. The above potential practice applications should therefore be seen as something to be mindful of when working with clients where cortisol and testosterone levels are relevant to their protocol.
Considerations for future research:
Future research should consider:
- Since LC diets have been shown to have a positive effect on health – decreased triglycerides, increased high density lipoprotein cholesterol and weight loss - future studies would benefit from including these markers so any positive and negative impacts can be monitored directly.
- Despite extensive analysis including sensitivity analysis to reduce bias and heterogeneity of the results, the paper highlights a need for further research to ensure consistency in key parameters e.g., exercise duration and intensity, carbohydrate supplements inclusion and period of dietary intervention. Since it was identified that HP-LP diets impact post exercise and resting TT, follow up studies would benefit from consistency in participants diets. This would help to reduce any potential confounding results.
Abstract
Background: Low-carbohydrate diets may have endocrine effects, although individual studies are conflicting. Therefore, a review was conducted on the effects of low- versus high-carbohydrate diets on men's testosterone and cortisol. Methods: The review was registered on PROSPERO (CRD42021255957). The inclusion criteria were: intervention study, healthy adult males, and low-carbohydrate diet: ≤35% carbohydrate. Eight databases were searched from conception to May 2021. Cochrane's risk of bias tool was used for quality assessment. Random-effects, meta-analyses using standardized mean differences and 95% confidence intervals, were performed with Review Manager. Subgroup analyses were conducted for diet duration, protein intake, and exercise duration. Results: Twenty-seven studies were included, with a total of 309 participants. Short-term (<3 weeks), low- versus high-carbohydrate diets moderately increased resting cortisol (0.41 [0.16, 0.66], p < 0.01). Whereas, long-term (≥3 weeks), low-carbohydrate diets had no consistent effect on resting cortisol. Low- versus high-carbohydrate diets resulted in much higher post-exercise cortisol, after long-duration exercise (≥20 min): 0 h (0.78 [0.47, 1.1], p < 0.01), 1 h (0.81 [0.31, 1.31], p < 0.01), and 2 h (0.82 [0.33, 1.3], p < 0.01). Moderate-protein (<35%), low-carbohydrate diets had no consistent effect on resting total testosterone, however high-protein (≥35%), low-carbohydrate diets greatly decreased resting (-1.08 [-1.67, -0.48], p < 0.01) and post-exercise total testosterone (-1.01 [-2, -0.01] p = 0.05). Conclusions: Resting and post-exercise cortisol increase during the first 3 weeks of a low-carbohydrate diet. Afterwards, resting cortisol appears to return to baseline, whilst post-exercise cortisol remains elevated. High-protein diets cause a large decrease in resting total testosterone (∼5.23 nmol/L).
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Timing of daily calorie loading affects appetite and hunger responses without changes in energy metabolism in healthy subjects with obesity.
Ruddick-Collins, LC, Morgan, PJ, Fyfe, CL, Filipe, JAN, Horgan, GW, Westerterp, KR, Johnston, JD, Johnstone, AM
Cell metabolism. 2022;34(10):1472-1485.e6
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Recent research has shown that the time of the day when a larger meal is consumed may influence energy utilisation, positively affecting weight loss. This randomised, crossover, isocaloric and eucaloric controlled feeding trial compared morning-loaded calorie intake with evening-loaded calorie intake to assess its effects on weight and metabolism. Thirty healthy, overweight, or obese individuals participated in this study for four weeks and assessed their energy intake and energy expenditure. Based on the findings of this study, there were no discernible variations in either resting metabolic rate or total energy expenditure based on the timing of energy intake. Morning loaded diet can significantly lower hunger and improve satiety compared to the evening-loaded diet. Because of these effects, a morning-loaded diet may aid weight loss through behavioural adaptations. Healthcare professionals can use the results of this study to understand the benefits of morning-loaded calorie intake in terms of hunger suppression and increased satiety which may promote weight loss through behavioural change. Further robust studies are required to evaluate the metabolic outcomes and energy metabolism followed by morning-loaded energy intake and evening-loaded energy intake.
Abstract
Morning loaded calorie intake in humans has been advocated as a dietary strategy to improve weight loss. This is also supported by animal studies suggesting time of eating can prevent weight gain. However, the underlying mechanisms through which timing of eating could promote weight loss in humans are unclear. In a randomized crossover trial (NCT03305237), 30 subjects with obesity/overweight underwent two 4-week calorie-restricted but isoenergetic weight loss diets, with morning loaded or evening loaded calories (45%:35%:20% versus 20%:35%:45% calories at breakfast, lunch, and dinner, respectively). We demonstrate no differences in total daily energy expenditure or resting metabolic rate related to the timing of calorie distribution, and no difference in weight loss. Participants consuming the morning loaded diet reported significantly lower hunger. Thus, morning loaded intake (big breakfast) may assist with compliance to weight loss regime through a greater suppression of appetite.
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Effect of a Personalized Diet to Reduce Postprandial Glycemic Response vs a Low-fat Diet on Weight Loss in Adults With Abnormal Glucose Metabolism and Obesity: A Randomized Clinical Trial.
Popp, CJ, Hu, L, Kharmats, AY, Curran, M, Berube, L, Wang, C, Pompeii, ML, Illiano, P, St-Jules, DE, Mottern, M, et al
JAMA network open. 2022;5(9):e2233760
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Plain language summary
Postprandial glycaemic response (PPGR) to foods can be different from person to person. This could be the reason why people experience different weight loss outcomes with standardised diets such as a low glycaemic index diet, low-fat diet or a low carbohydrate diet. In this single-centre, population-based, randomised, blinded clinical trial, 204 participants with irregular glucose metabolism and obesity were randomised to consume either a low-fat or personalised diet for six months in combination with fourteen behavioural change counselling sessions. The participants in the personalised diet group received a colour-coded meal score to indicate their estimated PPGR for different foods. The results of this study showed no significant weight reduction in the personalised diet group compared to the low-fat diet. Further robust studies are required to develop appropriate precision nutrition interventions for weight loss and energy balance. However, healthcare professionals can use the results of this study to understand that both a low-fat diet and a personalised diet, coupled with behavioural counselling, may be effective in promoting weight loss in obese populations with irregular glucose metabolism.
Abstract
IMPORTANCE Interindividual variability in postprandial glycemic response (PPGR) to the same foods may explain why low glycemic index or load and low-carbohydrate diet interventions have mixed weight loss outcomes. A precision nutrition approach that estimates personalized PPGR to specific foods may be more efficacious for weight loss. OBJECTIVE To compare a standardized low-fat vs a personalized diet regarding percentage of weight loss in adults with abnormal glucose metabolism and obesity. DESIGN, SETTING, AND PARTICIPANTS The Personal Diet Study was a single-center, population-based, 6-month randomized clinical trial with measurements at baseline (0 months) and 3 and 6 months conducted from February 12, 2018, to October 28, 2021. A total of 269 adults aged 18 to 80 years with a body mass index (calculated as weight in kilograms divided by height in meters squared) ranging from 27 to 50 and a hemoglobin A1c level ranging from 5.7% to 8.0% were recruited. Individuals were excluded if receiving medications other than metformin or with evidence of kidney disease, assessed as an estimated glomerular filtration rate of less than 60 mL/min/1.73 m2 using the Chronic Kidney Disease Epidemiology Collaboration equation, to avoid recruiting patients with advanced type 2 diabetes. INTERVENTIONS Participants were randomized to either a low-fat diet (<25% of energy intake; standardized group) or a personalized diet that estimates PPGR to foods using a machine learning algorithm (personalized group). Participants in both groups received a total of 14 behavioral counseling sessions and self-monitored dietary intake. In addition, the participants in the personalized group received color-coded meal scores on estimated PPGR delivered via a mobile app. MAIN OUTCOMES AND MEASURES The primary outcome was the percentage of weight loss from baseline to 6 months. Secondary outcomes included changes in body composition (fat mass, fat-free mass, and percentage of body weight), resting energy expenditure, and adaptive thermogenesis. Data were collected at baseline and 3 and 6 months. Analysis was based on intention to treat using linear mixed modeling. RESULTS Of a total of 204 adults randomized, 199 (102 in the personalized group vs 97 in the standardized group) contributed data (mean [SD] age, 58 [11] years; 133 women [66.8%]; mean [SD] body mass index, 33.9 [4.8]). Weight change at 6 months was -4.31% (95% CI, -5.37% to -3.24%) for the standardized group and -3.26% (95% CI, -4.25% to -2.26%) for the personalized group, which was not significantly different (difference between groups, 1.05% [95% CI, -0.40% to 2.50%]; P = .16). There were no between-group differences in body composition and adaptive thermogenesis; however, the change in resting energy expenditure was significantly greater in the standardized group from 0 to 6 months (difference between groups, 92.3 [95% CI, 0.9-183.8] kcal/d; P = .05). CONCLUSIONS AND RELEVANCE A personalized diet targeting a reduction in PPGR did not result in greater weight loss compared with a low-fat diet at 6 months. Future studies should assess methods of increasing dietary self-monitoring adherence and intervention exposure. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT03336411.