1.
Distribution of energy intake across the day and weight loss: A systematic review and meta-analysis.
Young, IE, Poobalan, A, Steinbeck, K, O'Connor, HT, Parker, HM
Obesity reviews : an official journal of the International Association for the Study of Obesity. 2023;24(3):e13537
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Plain language summary
Obesity increases an individual's risk of metabolic disease, such as diabetes and cardiovascular disease, musculoskeletal disorders such as osteoarthritis, and some cancers. “Chrononutrition” relates to the timing of meals and distribution of total energy intake across the day. Evidence is building chrononutrition as a potential target in both weight loss and metabolic disease interventions. The aim of this study was to examine the impact of earlier versus later distribution of total daily energy intake on weight loss, and to evaluate the potential for utilizing altered energy distribution as a tool in weight loss interventions. This study is a systematic review and meta-analysis of nine clinical studies. Total number of participants was 485 (earlier distributed total energy intakes: n = 244, later distributed total energy intakes; n = 241). Results show that energy intakes with a focus on earlier distribution resulted in significantly greater weight loss when compared with similarly energy-restricted diets with individuals consuming a larger proportion of their total energy intake later in the day and into the evening. Authors conclude that earlier energy intakes may be a promising tool to be used in conjunction with other weight loss strategies such as energy restriction to enhance weight loss. However, further research is required to elucidate the additional positive impacts that earlier distributed total energy intakes may have on weight and metabolic health.
Expert Review
Conflicts of interest:
None
Take Home Message:
Implementing a dietary strategy where a higher proportion of energy is consumed earlier in the day may offer additional benefits to an energy restricted diet for weight loss, blood glucose, improve markers of insulin resistance, increase satiety and improve hunger management. Based on the findings, earlier distribution of energy intake may serve as an effective component of a weight loss protocol.
Evidence Category:
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X
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:
Background
Chrononutrition refers to the timing and distribution of total daily energy intake across the day. It has been proposed that consuming a greater proportion of total daily energy intake earlier in the day as opposed to the evening may be beneficial for weight loss and metabolic health.
Aims
This systematic review and meta-analysis aimed to assess the impact of earlier versus later distribution of total daily energy intake on weight loss.
Results
A total of 9 randomised controlled trials involving 485 participants were included in this analysis. The study durations ranged from 5-16 weeks. All of the studies included in this analysis applied energy-restricted diets to both intervention arms. The mean percentages of energy intake in 8 of the 9 studies per meal were:
- Earlier distributed intakes: breakfast: 34% ± 16%, lunch: 38% ± 7%, dinner: 20% ± 6%.
- Later distributed intakes: breakfast: 19% ± 6%, lunch: 30% ± 10%, dinner; 40% ± 11%.
One of the studies advised percentage of energy intakes as either:
- Earlier: 70% for breakfast, morning tea and lunch and 30% for afternoon tea and dinner
- Late: 55% for breakfast, morning tea and lunch and 45% for afternoon tea and dinner.
The earlier distributed energy intake groups demonstrated significantly greater weight loss when compared with later distributed energy intake groups ( Mean Difference (MD) −1.23 kg; 95% CI −2.40, −0.06, p = 0.04;
I2 = 98%).
The earlier energy intake groups also displayed lower fasting and bedtime glucose levels (fasting: −0.83 vs. −0.27 mmol/L, p = 0.001; before sleep: −1.70 vs. −0.28 mmol/L, p = 0.009).
A random-effects model demonstrated that the earlier intake groups displayed greater reductions in LDL (MD: −0.11 mmol/L; 95% CI −0.14, −0.07, p < 0.01), fasting glucose (MD: 0.15 mmol/L, 95% CI −0.23, −0.06, p < 0.001) and HOMA-IR (MD: −0.38; 95% CI −0.64, −0.11, p = 0.005).
One study reported that earlier distribution energy intake also led to a greater reduction in medications following the intervention for type 2 diabetics (31% vs. 0%, P=0.002).
Two of the studies assessed both appetite and hunger and identified that earlier distribution of energy led to improvements in their urge to eat, preoccupation with food and cravings for sweets and fats.
Clinical practice applications:
Earlier distribution of energy intake may be beneficial for:
- Weight loss
- Improve fasting insulin, HOMA-IR, fasting glucose and HbA1c
- Reducing LDL
- Improving satiety and hunger management
- Supporting the reduction of medications for individuals with type 2 diabetes
- Improving regularity of sleep and waking times
Considerations for future research:
As the included studies only ranged from 5-16 weeks, longer duration studies would be useful to identify the effect of earlier distribution of energy intake on body weight, metabolic health and appetite over a longer period of time. There was a high degree of heterogeneity between the studies and a lack of uniformity in the distributions of energy intake across the day. Further studies with more uniformity of energy distribution would be needed to identify the optimal distribution of energy across the day to improve body weight and metabolic health.
Abstract
Consuming a greater proportion of total energy intake earlier in the day rather than in the evening is proposed to positively influence weight loss and health, potentially due to greater synchronization of human body circadian rhythms. This systematic review provides an update on existing evidence regarding earlier distributed eating patterns in weight loss interventions. Using a robust search strategy in five electronic databases, nine randomized controlled trials investigating the impact of energy intake distribution on weight loss were identified. Following critical appraisal, a random-effects meta-analyses found that, in the context of an energy-reduced diet, distributing energy intake with a focus on earlier intake resulted in significantly greater weight loss (-1.23 kg; 95% CI 2.40, -0.06, p = 0.04). Improvements in HOMA-IR, fasting glucose, and LDL cholesterol were also seen. The current study provides a timely update on the evidence linking distribution of total daily energy intake and health, showing that a focus on earlier intakes can result in greater short-term weight loss compared with later intakes. Future studies are needed to elucidate the impact that earlier intakes may have on weight management and metabolic health.
2.
Effect of Intermittent Fasting Diet on Glucose and Lipid Metabolism and Insulin Resistance in Patients with Impaired Glucose and Lipid Metabolism: A Systematic Review and Meta-Analysis.
Yuan, X, Wang, J, Yang, S, Gao, M, Cao, L, Li, X, Hong, D, Tian, S, Sun, C
International journal of endocrinology. 2022;2022:6999907
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The prevalence of obesity and metabolic syndrome may increase the risk of cardiovascular disease (CVD), diabetes, and neurological conditions. The imbalance in glucose and lipid metabolism and hypertension characterises the development of these chronic diseases. Intermittent fasting (IF) has been considered an effective dietary strategy for reducing the risk of obesity, insulin resistance, dyslipidaemia, diabetes, and CVD. This systematic review and meta-analysis include ten randomised controlled trials to evaluate the effects of IF intervention on glucose and lipid metabolism in people with metabolic syndrome. IF intervention regulated glucose metabolism by improving fasting blood glucose, glycosylated haemoglobin, insulin, and insulin resistance. IF intervention also positively impacted the body mass index and waist circumference. The total cholesterol, low-density lipoprotein levels, and triglyceride levels also improved, followed by the IF, showing the impact on lipid metabolism. Further robust studies are required due to heterogeneity between the included studies in type of IF, duration, the health status of participants, ethnicity, and outcome measurements. However, healthcare professionals can use the results of this systematic review and meta-analysis to understand the therapeutic effect of IF intervention on glycolipid metabolism in people with metabolic syndrome.
Expert Review
Conflicts of interest:
None
Take Home Message:
- IF does not require calorie restriction which may result in greater compliance
- IF does not restrict macronutrients such as CHO and fats, so may avoid the exclusion of key nutrients e.g. healthy fats and wholegrains.
- IF may have fewer adverse effects on daily routines and quality of life, which may mean adherence is easier.
- Improved glucose and lipid metabolism may prevent the development of chronic health conditions such as T2D, CVD and cancer.
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:
Management of glucose and lipid metabolism can be achieved through weight reduction using dietary interventions such as very low calorie or CHO diets, which may be effective but difficult to sustain long term. An alternative approach for weight management, improved insulin resistance and subsequent prevention of comorbitities e.g. Type 2 Diabetes (T2D), Cardiovascular Disease (CVD) and cancer, is Intermittent Fasting (IF). such as time restricted or periodic fasting.
This study summarises the effects of IF dietary interventions lasting less than three months in overweight and obese women with Metabolic Syndrome, defined as the presence of any metabolic dysfunction including obesity, hyperglycaemia, dyslipidaemia or hypertension.
The meta-anlaysis was carried out following PRISMA guidelines. A literature search in PubMed and Medline using the keywords obesity/overweight, IF diet, metabolic syndrome, RCT’s and humans resulted in 10 studies with 12 types of intervention for analysis. The following outcomes were evaluated: glucose and lipid metabolism, insulin resistance, weight loss and blood pressure.
Results were analysed in R software using mean differences and 95% confidence intervals, and either random or fixed effects depending on the Cochrane’s Q and I(2) statistics. Funnel plots were inspected for potential bias and Egger’s regression tests for publication bias.
There were significant differences before and after the interventions for all glucose and lipid metabolism markers as well as body weight and systolic blood pressure :
Glucose metabolism:
- Fasting glucose reduced by 0.15mmol/L
- Insulin plasma reduced by 13.25uUI
- HbA1c reduced by 0.08%
- HOMA-IR (insulin resistance index) reduced by 0.31 on average
Lipid metabolism:
- Total cholesterol reduced by 0.32mmol/L
- LDL reduced by 0.22mmol/L
- Triglyceride reduced by 0.04mmol/L
Weight loss:
- Body weight reduced by 1.87kg
- BMI reduced by 0.8kg/m2
- Waist circumference reduced by 2.08cm
Blood pressure:
- Systolic reduced by 2.58mmHg
- Diastolic reduced by 3.12mmHg
Despite limitations of the meta-analysis, this study demonstrates IF has therapeutic effects on those with disordered lipid and glucose metabolism, and may prove to be an effective and sustainable approach.
Clinical practice applications:
- IF may be an effective alternative to restricted calorie or CHO diets for weight management with the associated benefits of glucose and lipid metabolism.
- IF has been shown to have therapeutic effects on individuals with impaired glucose and lipid metabolism.
- IF may be considered as a sustainable lifestyle choice rather than a ‘weight loss’ programme such as a very low calorie diet, which can result in poor quality of life and subsequent reduced adherence.
- Since it may take time for impaired glucose and lipid metabolism to progress to more serious disease states, establishing IF as an early intervention, may be considered as a prudent form of preventative medicine.
- IF has shown to have other health benefits such as reduced blood pressure and may be considered as adjuvant therapy.
Considerations for future research:
- Compares the effects of IF on different ethnicities, sex and age categories
- Evaluates the effect of IF on other disease states e.g. cancer, auto-immune conditions
- Assesses the response of other biomarkers e.g. inflammatory cytokines
- Compares different types and durations of IF on health biomarkers (eg periodic, time restricted)
Abstract
The question of whether or not intermittent fasting diets improve the clinical indicators of glycolipid metabolism remains unclear. This study systematically reviewed the relevant clinical trials to evaluate the effects of intermittent fasting diet on glucose and lipid metabolism and insulin sensitivity in patients with metabolic syndrome. To evaluate the effect of intermittent fasting diet intervention on patients with disorders of glucose and lipid metabolism, random-effect or fixed-effect meta-analysis models were used to calculate the average difference before and after intermittent fasting diet intervention and the corresponding 95% confidence intervals (CIs). After intermittent fasting diet intervention, in terms of glucose metabolism, fasting blood glucose reduced by 0.15 mmol/L (95% CI: -0.23; -0.06), glycosylated hemoglobin reduced by 0.08 (95% CIs: -0.25; -0.10), insulin plasma levels reduced by 13.25 uUI (95% CIs: -16.69; -9.82), and HOMA-IR decreased by 0.31 on an average (95% CIs: -0.44; -0.19). In addition, BMI decreased by 0.8 kg/m2 (95% CIs: -1.32; -0.28), body weight reduced by 1.87 kg (95% CIs: -2.67; -1.07), and the waist circumference decreased by 2.08 cm (95% CIs: -3.06; -1.10). Analysis of lipid metabolism showed that intermittent fasting diet intervention effectively reduced the total cholesterol level by 0.32 mmol/L (95% CIs: -0.60; -0.05), low-density lipoprotein level by 0.22 mmol/L (95% CIs: -0.37; -0.07), and triglyceride level by 0.04 mmol/L (95% CIs: -0.15; -0.07). Intermittent fasting diets have certain therapeutic effects on blood glucose and lipids in patients with metabolic syndrome and significantly improve insulin resistance. It may be considered as an auxiliary treatment to prevent the occurrence and development of chronic diseases.
3.
Effects of Oat Beta-Glucan Intake on Lipid Profiles in Hypercholesterolemic Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Yu, J, Xia, J, Yang, C, Pan, D, Xu, D, Sun, G, Xia, H
Nutrients. 2022;14(10)
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Dyslipidaemia is one of the risk factors associated with cardiovascular disease. Beta-glucan is a viscous soluble fibre found in microalgae, fungi and grains like oats, barley, sorghum etc. This systematic review and meta-analysis included thirteen randomised controlled trials to evaluate the effectiveness of oat beta-glucans on the lipid profiles of patients with hypercholesterolemia. This research showed a significant reduction in total cholesterol and low-density lipoprotein levels in hypercholesterolemic adults after beta-glucan intake. However, beta-glucans did not impact triglyceride and high-density lipoprotein cholesterol. Beta-glucan's effect on lipid profiles depended on the severity of hypercholesterolemia, the duration of the intervention, the source of beta-glucan, and the dosage of beta-glucan. Healthcare professionals can use the results of this study to understand the lipid profile-improving effects of beta-glucans in adults with moderate hypercholesterolemia. However, further robust studies are required to evaluate the effects of beta-glucan on lipid profiles and how the effect is affected by gender differences.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Consumption of oat beta glucans may be beneficial for improving total cholesterol and LDL-c in people with mild and moderate hypercholesterolemia
- The U.S Food and Drug Administration (FDA) recommends 3g or more of oat beta glucans per day to reap the benefits. This could be from 90g of oats (3 x 30g portions) or 1 30g portion of oats, 3 oatcakes and 1-2 tbsp of oat bran.
Evidence Category:
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X
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:
Authors highlight that Hypercholesterolemia is a risk factor for cardiovascular disease and a symptom of Metabolic Syndrome. Hypercholesterolemia commonly includes; elevated levels of total cholesterol and low-density lipoprotein cholesterol (LDL-c) and lower levels of high-density lipoprotein cholesterol (HDL-c).
Conventional medical treatment for hypercholesterolemia is statins, however, statins can have a number of adverse side effects. For this reason, dietary interventions have been investigated including the use of oat beta-glucans for their potential lipid lowering effects.
The aim of this systematic review and meta-analysis was to synthesise and evaluate the evidence for the effects of oat beta-glucans on serum cholesterol and triglyceride (TG) levels in adults with hypercholesterolemia.
Thirteen randomised controlled trials (RCTs) published between 1999 – 2021 met the study inclusion criteria. These studies included a total population of 927 people aged between 38-76 years and from 7 different countries worldwide. The majority of participants were diagnosed with mild hypercholesterolemia.
Participants were randomised into an intervention group receiving dietary sources of oat beta-glucans or food with added oat beta-glucans or a placebo control group consisting of diets without beta-glucans.
Study lengths ranged from 3 to 8 weeks with doses of oat beta-glucans between 1.5g to 6g. The studies were also broken down into sub-groups for high and low doses of oat beta-glucan and mild and moderate hypercholesterolemia.
Baseline and endpoint cholesterol (total cholesterol C, HD-c & LDL-c) and triglycerides were used to assess the effectiveness of the interventions and a weighted mean difference (WMD) calculated with a 95% confidence interval (CI).
Key Findings:
- a reduction in total cholesterol (WMD = -0.24mmol/L; 95% CI)
- a reduction in LDL-c (WMD = -0.27mmol/L; 95% CI )
- Sub-groups found that oat beta-glucans reduced serum TG levels in patients with moderate hypercholesterolemia (WMD = -0.11 mmol/L; 95% CI) but not in cases of mild hypercholesterolemia. (WMD = -0.01 mmol/L; 95% CI)
- Higher daily doses of oat beta glucans had more positive effects on TG levels, however the results were not statistically significant in this meta-analysis
- <3g WMD -0.11 mmol/L; 95% CI: -0.13 to -0.08 mmol/L
- >3g WMD -0.00 mmol/L; 95% CI: -0.16 to -0.16 mmol/L
- Greater reductions in HDL -c were found in patients with moderate hypercholesterolemia (WMD-0.06 mmol/L; 95% CI; -0.07 to -0.05 mmol/L) compared to mild cases (WMD-0.01 mmol/L; 95% CI; -0.08 to -0.10 mmol/L).
Conclusion
Dietary intake of oat beta-glucans may support the reduction of total cholesterol and low density lipoprotein cholesterol, however, no significant changes were found for high density lipoprotein cholesterol or serum triglycerides. Due to the heterogeneity between studies and inconsistencies in results, more trials are needed with larger sample sizes and longer durations.
Notes: The authors reported no conflicts of interest.
Clinical practice applications:
Based on the pooled results of this meta-analysis:
- 1.5g -6g of dietary intake of oat beta-glucans could support a reduction of TC and LDL-c in cases of mild and moderate hypercholesterolemia
- Intake of oat beta glucans >3g may reduce TG levels
- HDl -c may be improved with oat beta glucan intake of between 1.5g to 6g for clients with moderate hypercholesterolemia.
Considerations for future research:
The findings of 8 of the 13 RCTs indicated that when compared to the control group, LDL-c could be lowered by oat beta-glucans whilst the other 5 trials did not. However, the cumulative results of this meta analysis found a reduction in LDL-c.
There were also several limitations to this study:
- Heterogeneity between studies and inconsistent results
- Short study duration
- Small populations and limited sample size
- The results varied for different levels of hypercholesterolemia
- Results may also differ by sex and source of oat beta glucans
Larger and longer trials are therefore needed to confirm the results.
Abstract
(1) Background: hyperlipidemia is one of the cardiovascular diseases which becomes a great threat to the health of people worldwide. Oat beta-glucan is reported to have a beneficial effect on lowering blood lipids. To probe the effect of oat beta-glucan consumption on serum lipid profiles (total cholesterol, total triglyceride, high-density lipoprotein-cholesterol, and low-density lipoprotein-cholesterol), we carried out a systematic search on randomized controlled trials of oat beta-glucan intervention on hypercholesterolemic individuals. (2) Methods: the pieces of literature were obtained from PubMed, Scopus, Cochrane Library, Web of Science, and the Embase from inception to 28 February 2022. The results were presented with the weighted mean difference (WMD) with a 95% CI. The random-effects or fixed-effects model was applied according to the heterogeneity. The subgroup analysis and meta-regression were used to identify the source of heterogeneity. (3) Results: thirteen trials with 927 participants were included in our meta-analysis. Overall, oat beta-glucan supplementation significantly reduced levels of TC (pooled WMD = -0.24 mmol/L; 95%CI: -0.28 to -0.20 mmol/L), LDL-c (pooled WMD = -0.27 mmol/L; 95%CI: -0.35 to -0.20 mmol/L). Furthermore, beta-glucan consumption did not show significant effects on TG (pooled WMD = -0.04 mmol/L; 95%CI: -0.13 to 0.05 mmol/L), HDL-c (pooled WMD = 0.00 mmol/L; 95%CI: -0.05 to 0.05 mmol/L). Subgroup analysis indicated that critical factors, such as disease severity of participants, the daily intervention of oat beta-glucan, source of oat beta-glucan, and duration of intervention had impacts on outcomes. (4) Conclusions: oat beta-glucan intake may significantly decrease the level of TC and LDL-c while no significant changes in TG and HDL-c were observed. This meta-analysis supports the health benefits of oat beta-glucan, especially for its cholesterol-lowering features, although it has some inevitable limitations.