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A lower-carbohydrate, higher-fat diet reduces abdominal and intermuscular fat and increases insulin sensitivity in adults at risk of type 2 diabetes

19 / 02 / 15

Gower AB et al compared carbohydrate-restricted diets with low-fat diets in two populations at elevated risk of type-2 diabetes (T2D): overweight/obese/pre-diabetic adults, and women with polycystic ovary syndrome (PCOS).

Two intervention studies were conducted:

Study 1 (overweight/obese participants): Crossover intervention study with two 8-week intervention phases and a 4-week wash out. Participants were assigned to one of two diets: CHO 55% or 43%; fat 27% or 39%. Protein was kept constant at 18% energy in both diets. During the first 8-week period all food was provided at a eucaloric level.

Main measure outcomes: Serum insulin, glucose, body composition, fat distribution and circulating markers of inflammation.

Result:  In the eucaloric phase, loss of intra-abdominal adipose tissue (IAAT) was significantly greater in the low CHO group (P<0.05)

Study 2 (polycystic ovary syndrome participants): Crossover intervention study with two 8-week arms and a 4-week wash out. Participants were randomised to one of two diets: 40%; CHO 55% or fat 27% or 41%; protein 18% or 19% energy.

Main measure outcomes: Fasting glucose, fasting insulin, insulin sensitivity, b-cell responsiveness, body composition and body fat distribution

Result: The lower CHO diet resulted in decreased fasting insulin (P<0.001)

Among two groups of individuals at elevated risk of T2D (overweight /obese/prediabetic adults, and women with PCOS) restriction of dietary carbohydrate relative to restriction of dietary fat resulted in favourable changes in body composition, fat distribution and glucose metabolism that may reduce the risk of T2D.

Limitations: Study 1 found changes in weight loss during the eucaloric phase when no change in weight loss should have been seen between diets if calories did not change. Study is specific to US population.