Diabetes, Obesity

Effects of Ketogenic and Low-Carbohydrate Diets on Body Composition in Overweight and Obese Adults: A Systematic Review and Meta-Analysis of RCTs

A recent systematic review and meta-analysis examined how ketogenic diets (KD) and low-carbohydrate diets (LCD) affect body weight, body mass index (BMI), fat mass, and body fat percentage in adults with overweight or obesity. The analysis included 33 randomized controlled trials (RCTs) with a total of 2,821 participants.

Since the studies varied in nutrition interventions and participant characteristics, the researchers used a statistical method to balance these differences. They also conducted additional analyses to see how factors like diet duration, carbohydrate intake, and health conditions such as type 2 diabetes (T2DM) affected the results.

Results:

• Overall findings:

→KD/LCD significantly reduced body weight, BMI, and body fat percentage but did not significantly impact fat mass.

→Heterogeneity across studies was high due to varying intervention types and participant characteristics.

• Effects by duration of KD/LCD:

→ Body weight reduction was significant for interventions lasting ≥1 month.

→ Fat mass reduction was significant at 1 and 4–6 months, but not at other time points.

→ Body fat percentage reductions were notable after 4–12 months of diet adherence.

• Effects by carbohydrate intake:

→ Body weight and BMI reductions were significant in individuals consuming ≤50 g/day.

→ Fat mass was significantly reduced in groups consuming ≤20 g/day and 81–100 g/day.

→ Body fat percentage reductions were significant in those consuming 21–50 g/day.

• Effects in Individuals with T2DM:

→ Significant body weight and BMI reductions were observed with a carbohydrate intake of ≤20 g/day for 3 months.

Ketogenic and low-carb diets are effective in reducing body weight, BMI, and body fat percentage when followed for at least 1 month. Carbohydrate intake of <50 grams per day was most effective across all measured outcomes. Future research should focus on long-term effects, macronutrient balance, and adherence strategies, particularly for individuals with T2DM.