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Effect of a Low-Fat Vegan Diet on Body Weight, Insulin Sensitivity, Postprandial Metabolism, and Intramyocellular and Hepatocellular Lipid Levels in Overweight Adults: A Randomized Clinical Trial.
Kahleova, H, Petersen, KF, Shulman, GI, Alwarith, J, Rembert, E, Tura, A, Hill, M, Holubkov, R, Barnard, ND
JAMA network open. 2020;3(11):e2025454
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Obesity is uncommon in individuals on a plant-based diet, possibly due to the high-fiber low fat nature of this style of eating and due to the fact that low levels of fat may increase metabolism levels. The aim of this randomised control trial of 244 people following a vegan diet was to assess the effects of a low-fat vegan diet on body weight, insulin resistance (IR), metabolism and lipid levels in the liver and muscle over 16 weeks. The results showed that individuals who followed the low-fat vegan diet as opposed to a normal vegan diet lost more weight, attributed to a loss of body fat and had decreased cholesterol levels. Measures of how the body balances blood sugars were improved and this was directly related to weight loss. The amount of energy needed to digest the food in the intervention diet was increased compared to the control group and this was involved in a relationship whereby as fat mass decreased, blood sugar balance improved, and metabolism increased. Liver lipids decreased in the intervention group, which was directly related to body weight loss and as liver lipids decreased, blood sugar balance increased. Muscle lipids were significantly decreased in the intervention group compared to the control group. It was shown that as fat mass decreased, muscle fat levels and blood sugar balance improved. It was concluded that the low-fat plant-based diet reduced body weight due to a reduced energy intake and increased body metabolism following eating. Blood sugar control was improved due to reduced fat levels in the muscles and liver. This study could be used by healthcare professionals to recommend a low-fat plant based diet to individuals who are overweight and/or who are showing signs of blood sugar imbalance.
Abstract
Importance: Excess body weight and insulin resistance lead to type 2 diabetes and other major health problems. There is an urgent need for dietary interventions to address these conditions. Objective: To measure the effects of a low-fat vegan diet on body weight, insulin resistance, postprandial metabolism, and intramyocellular and hepatocellular lipid levels in overweight adults. Design, Setting, and Participants: This 16-week randomized clinical trial was conducted between January 2017 and February 2019 in Washington, DC. Of 3115 people who responded to flyers in medical offices and newspaper and radio advertisements, 244 met the participation criteria (age 25 to 75 years; body mass index of 28 to 40) after having been screened by telephone. Interventions: Participants were randomized in a 1:1 ratio. The intervention group (n = 122) was asked to follow a low-fat vegan diet and the control group (n = 122) to make no diet changes for 16 weeks. Main Outcomes and Measures: At weeks 0 and 16, body weight was assessed using a calibrated scale. Body composition and visceral fat were measured by dual x-ray absorptiometry. Insulin resistance was assessed with the homeostasis model assessment index and the predicted insulin sensitivity index (PREDIM). Thermic effect of food was measured by indirect calorimetry over 3 hours after a standard liquid breakfast (720 kcal). In a subset of participants (n = 44), hepatocellular and intramyocellular lipids were quantified by proton magnetic resonance spectroscopy. Repeated measure analysis of variance was used for statistical analysis. Results: Among the 244 participants in the study, 211 (87%) were female, 117 (48%) were White, and the mean (SD) age was 54.4 (11.6) years. Over the 16 weeks, body weight decreased in the intervention group by 5.9 kg (95% CI, 5.0-6.7 kg; P < .001). Thermic effect of food increased in the intervention group by 14.1% (95% CI, 6.5-20.4; P < .001). The homeostasis model assessment index decreased (-1.3; 95% CI, -2.2 to -0.3; P < .001) and PREDIM increased (0.9; 95% CI, 0.5-1.2; P < .001) in the intervention group. Hepatocellular lipid levels decreased in the intervention group by 34.4%, from a mean (SD) of 3.2% (2.9%) to 2.4% (2.2%) (P = .002), and intramyocellular lipid levels decreased by 10.4%, from a mean (SD) of 1.6 (1.1) to 1.5 (1.0) (P = .03). None of these variables changed significantly in the control group over the 16 weeks. The change in PREDIM correlated negatively with the change in body weight (r = -0.43; P < .001). Changes in hepatocellular and intramyocellular lipid levels correlated with changes in insulin resistance (both r = 0.51; P = .01). Conclusions and Relevance: A low-fat plant-based dietary intervention reduces body weight by reducing energy intake and increasing postprandial metabolism. The changes are associated with reductions in hepatocellular and intramyocellular fat and increased insulin sensitivity. Trial Registration: ClinicalTrials.gov Identifier: NCT02939638.
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Role of Calcium and Low-Fat Dairy Foods in Weight-Loss Outcomes Revisited: Results from the Randomized Trial of Effects on Bone and Body Composition in Overweight/Obese Postmenopausal Women.
Ilich, JZ, Kelly, OJ, Liu, PY, Shin, H, Kim, Y, Chi, Y, Wickrama, KKAS, Colic-Baric, I
Nutrients. 2019;11(5)
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A woman’s menopausal years are believed to bring about weight gain due to various biological mechanisms, such as depletion of oestrogen. Many women undertake weight loss diets, in an attempt to control the weight gain, and although weight loss can reduce the risk factors for metabolic and cardiovascular disease etc, it can also lead to accelerated loss bone density and muscle mass. The objective of this study was to investigate whether by complementing a low-calorie diet with 4 to 5 servings of low-fat dairy foods per day and/or supplementing with calcium and vitamin D supplements would aid weight loss and preserve either/both bone and muscle mass. The study was conducted on 189 early postmenopausal, obese women. It was a randomized, placebo-controlled clinical trial conducted over 6 months. Researchers found that results were better for the participants on the low-fat dairy foods and those supplementing with calcium and vitamin D when compared to the placebo group (who only had placebo pills). They suggest that when embarking on a weight loss program it is beneficial to include 4 to 5 servings of low-fat dairy foods each day and take calcium and vitamin D supplements will have a positive impact on weight loss, bone density and muscle mass in post-menopausal women.
Abstract
Several studies have investigated the possibility of dairy foods and calcium (Ca) mediating weight and body composition, but a consensus has not been reached. We aimed to investigate weight-loss-related outcomes during intervention with low-fat dairy foods or Ca + vitamin D supplements, both as complements to hypocaloric diets. Overweight/obese Caucasian, early-postmenopausal women (n = 135) were recruited for a 6 month energy-restricted weight loss study complemented with either low-fat dairy foods (D; 4-5 servings/day), or Ca + vitamin D supplements (S); both to amount a total of ~1500 mg/day and 600 IU/day of Ca and vitamin D, respectively, or placebo pills (C). Bone mineral density (BMD) and lean and fat tissue were measured by Lunar iDXA. Serum and urinary markers of bone turnover were analyzed. Diet and physical activity were assessed with 3-day records. Participants on average lost ~4%, ~3%, and ~2% of body weight, fat, and lean tissue, respectively. The significantly better outcomes were noticed in participants in the D group regarding body composition (fat loss/lean tissue preservation) and in participants in the S group regarding the BMD outcomes, compared to those in the C group. Therefore, increasing low-fat dairy foods to 4-5 servings/day and/or increasing Ca & vitamin D intake by supplements (in those who are at the borderline dietary intake) may be beneficial for weight loss/maintenance and may lead to more favorable bone and body composition outcomes in postmenopausal women during moderate weight loss.
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A Randomized Study of the Effects of Additional Fruit and Nuts Consumption on Hepatic Fat Content, Cardiovascular Risk Factors and Basal Metabolic Rate.
Agebratt, C, Ström, E, Romu, T, Dahlqvist-Leinhard, O, Borga, M, Leandersson, P, Nystrom, FH
PloS one. 2016;11(1):e0147149
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Fruits and vegetables intake has been advocated to improve blood lipids profile and reduce risk of cardiovascular disease, diabetes and cancer. However, a low fat diet rich in fruits and vegetables has showed no effect on cardiovascular disease and cancer in a large randomized American trial. This might be due to the high sugar content in fruits, particularly fructose. The aim of this study was to compare the effects of adding either fruits or nuts to the diet of 30 healthy non-obese individuals on liver fat, metabolic rate and cardiovascular risk markers. Authors concluded that the trial only showed small effects on cardiovascular risk factors. Nevertheless, there was a significant change in lipoprotein (fats that transport fats in the blood) levels between the two groups, which tends to give an advantage to the consumption of nuts over fruits. They deduced that increased intake of fruits doesn’t negatively impact cardiovascular disease risk factors in healthy non-obese individuals. However, further research needs to evaluate the effects on obese and insulin-resistant participants.
Abstract
BACKGROUND Fruit has since long been advocated as a healthy source of many nutrients, however, the high content of sugars in fruit might be a concern. OBJECTIVES To study effects of an increased fruit intake compared with similar amount of extra calories from nuts in humans. METHODS Thirty healthy non-obese participants were randomized to either supplement the diet with fruits or nuts, each at +7 kcal/kg bodyweight/day for two months. Major endpoints were change of hepatic fat content (HFC, by magnetic resonance imaging, MRI), basal metabolic rate (BMR, with indirect calorimetry) and cardiovascular risk markers. RESULTS Weight gain was numerically similar in both groups although only statistically significant in the group randomized to nuts (fruit: from 22.15 ± 1.61 kg/m(2) to 22.30 ± 1.7 kg/m(2), p = 0.24 nuts: from 22.54 ± 2.26 kg/m(2) to 22.73 ± 2.28 kg/m(2), p = 0.045). On the other hand BMR increased in the nut group only (p = 0.028). Only the nut group reported a net increase of calories (from 2519 ± 721 kcal/day to 2763 ± 595 kcal/day, p = 0.035) according to 3-day food registrations. Despite an almost three-fold reported increased fructose-intake in the fruit group (from 9.1 ± 6.0 gram/day to 25.6 ± 9.6 gram/day, p<0.0001, nuts: from 12.4 ± 5.7 gram/day to 6.5 ± 5.3 gram/day, p = 0.007) there was no change of HFC. The numerical increase in fasting insulin was statistically significant only in the fruit group (from 7.73±3.1 mIE/L to 8.81±2.9 mIE/L, p = 0.018, nuts: from 7.29±2.9 mIE/L to 8.62±3.0 mIE/L, p = 0.14). Levels of vitamin C increased in both groups while α-tocopherol/cholesterol-ratio increased only in the fruit group. CONCLUSIONS Although BMR increased in the nut-group only this was not linked with differences in weight gain between groups which potentially could be explained by the lack of reported net caloric increase in the fruit group. In healthy non-obese individuals an increased fruit intake seems safe from cardiovascular risk perspective, including measurement of HFC by MRI. TRIAL REGISTRATION ClinicalTrials.gov NCT02227511.
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Adolescent diet and subsequent serum hormones, breast density, and bone mineral density in young women: results of the Dietary Intervention Study in Children follow-up study.
Dorgan, JF, Liu, L, Klifa, C, Hylton, N, Shepherd, JA, Stanczyk, FZ, Snetselaar, LG, Van Horn, L, Stevens, VJ, Robson, A, et al
Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology. 2010;19(6):1545-56
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Population and animal studies suggest that fat in the diet may have an influence on the development of breast cancer, but the results of studies in humans are inconsistent. This randomised controlled trial aimed to determine the effects of a lower-fat diet during childhood and adolescence on markers associated with breast cancer risk in adults. Female participants were initially recruited at age 8-10 years old, as part of a study to test the effects of lower-fat diets on cholesterol levels in children. The study diet limited total fat intake to 28% of calories (<8% saturated fat, <9% polyunsaturated fat, remainder monounsaturated), cholesterol was limited to 150mg/day and consumption of fibre was encouraged. The children followed the diet for 7 years, when the trial was terminated. This follow-up study was conducted 9 years later, when the participants were aged 25 to 29 years old. After adjusting for current diet, the lower-fat diet group had significantly higher oestradiol levels and bone mineral density. Progesterone concentrations and breast density did not differ between the two groups. The authors concluded that consumption of a lower-fat diet during adolescence does not appear to affect factors associated with breast cancer risk. Current diet may be more important than adolescent diet in determining hormone levels in premenopausal women.
Abstract
BACKGROUND Adolescent diet is hypothesized to influence breast cancer risk. We evaluated the long-term effects of an intervention to lower fat intake among adolescent girls on biomarkers that are related to breast cancer risk in adults. METHODS A follow-up study was conducted on 230 girls who participated in the Dietary Intervention Study in Children (DISC), in which healthy, prepubertal, 8 to 10 year olds were randomly assigned to usual care or to a behavioral intervention that promoted a reduced fat diet. Participants were 25 to 29 years old at follow-up visits. All tests of statistical significance are two-sided. RESULTS In analyses that did not take account of diet at the time of the follow-up visit, the only statistically significant treatment group difference was higher bone mineral content in intervention group participants compared with usual care group participants; their mean bone mineral contents were 2,444 and 2,377 g, respectively. After adjustment for current diet, the intervention group also had statistically significantly higher bone mineral density and luteal phase serum estradiol concentrations. Serum progesterone concentrations and breast density did not differ by treatment group in unadjusted or adjusted analyses. CONCLUSIONS Results do not support the hypothesis that consumption of a lower fat diet during adolescence reduces breast cancer risk via effects on subsequent serum estradiol and progesterone levels, breast density, or bone mineral density. It remains unclear, however, if the results are specific to the DISC intervention or are more broadly applicable. IMPACT Modest reductions in fat intake during adolescence are unlikely to lower later breast cancer risk via long-term effects on the biomarkers measured.