Key result
A Mediterranean/low-carbohydrate diet combined with physical activity significantly increased intramyocellular triacylglycerol by 56% over 18 months compared to other weight loss strategies.
Why the study?
Does a Mediterranean/low-carbohydrate diet combined with physical activity alter intramyocellular triacylglycerol accumulation compared to a low-fat diet in sedentary adults with abdominal obesity or dyslipidemia?
RCT (n=277)
Single-blind (fitness instructor and MRI observers blinded)
Randomized to low-fat or Mediterranean/low-carbohydrate diet, then re-randomized to physical activity or no physical activity
No
Does a Mediterranean/low-carbohydrate diet combined with physical activity alter intramyocellular triacylglycerol accumulation compared to a low-fat diet in sedentary adults with abdominal obesity or dyslipidemia?
A Mediterranean/low-carbohydrate diet combined with physical activity significantly increases intramyocellular triacylglycerol during moderate weight loss, but this increase is not independently associated with worsened cardiometabolic risk.
Answers are grounded in this paper and cite their sources.
Mediterranean/low-carb diet plus activity raises IMTG during weight loss; challenges presumed link to cardiometabolic harm in obese adults.
BACKGROUND: Intramyocellular triacylglycerol (IMTG) is utilized as metabolic fuel during exercise and is linked to insulin resistance, but the long-term effect of weight loss strategies on IMTG among participants with abdominal fat, remain unclear. METHODS: In an 18-month trial, sedentary participants with abdominal fat/dyslipidemia were randomized to either a low-fat (LF) or Mediterranean/low-carbohydrate (MED/LC) diet (including 28g·day-1 of walnuts). After 6-months, the participants were re-randomized to moderate intense physical activity (PA+) or non-physical activity (PA-). Magnetic resonance imaging (MRI) was used to quantify changes of IMTG, abdominal sub-depots, hepatic and intermuscular fats. RESULTS: Across the 277 participants [86% men, age = 48 years, body-mass-index (BMI) = 31kg/m2, visceral fat = 33%] 86% completed the 18-m trial. At baseline, women had higher IMTG than men (3.4% vs. 2.3%, p<0.001) and increased IMTG was associated with aging and higher BMI, visceral and intermuscular fats, HbA1c%, HDL-c and leptin(p<0.05), but not with intra-hepatic fat. After 18 month of intervention and a -3 kg mean weight loss, participants significantly increased IMTG by 25%, with a distinct effect in the MED/LCPA+ group as compared to the other intervention groups (57% vs. 9.5-18.5%, p<0.05). Changes in IMTG were associated with visceral and intermuscular fat, metabolic syndrome, insulin and leptin (p<0.05 for all), however, these associations did not remain after adjustment for visceral fat changes. CONCLUSIONS: Lifestyle strategies differentially affect IMTG accumulation; combination of exercise with decreased carbohydrate/increased unsaturated fat proportion intake greatly increase IMTG. Our findings suggest that increased IMTG during diet-induced moderate weight loss may not be directly related to cardiometabolic risk. TRIAL REGISTRATION: ClinicalTrials.gov NCT01530724.
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Gepner et al. (2017) conducted an RCT in Abdominal obesity or dyslipidemia (n=277). Mediterranean/low-carbohydrate diet with physical activity vs. Low-fat diet and/or no physical activity was evaluated on Change in intramyocellular triacylglycerol (IMTG) (0.56% absolute increase (56% relative change), 95% CI 0.21-0.91, p=0.002). A Mediterranean/low-carbohydrate diet combined with physical activity significantly increased intramyocellular triacylglycerol by 56% over 18 months compared to other weight loss strategies.
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