Long-Term Diets and Changes in Body Composition and Bone Mineral Density: A Systematic Review and Meta-analysis

Area of Science:

• Nutrition Science
• Metabolic Health
• Dietary Interventions

Background:

• Long-term effects of various diets on body composition (BC) and bone mineral density (BMD) are not well-established.
• Obesity and related metabolic disorders necessitate understanding dietary impacts on body composition and bone health.
• Systematic review registration: PROSPERO no. CRD42018103116.

Purpose of the Study:

• To systematically evaluate the long-term effects (≥12 months) of weight-loss inducing dietary interventions on body composition and bone mineral density.
• To compare the efficacy of different dietary patterns, including moderate macronutrient (MM), low-fat/high-carbohydrate (LFHC), and high-fat/low-carbohydrate (HFLC) diets.
• To assess the impact of these diets on fat mass, lean mass, and bone mineral density in adults with a body mass index (BMI) ≥25 kg/m².

Main Methods:

• Systematic literature search conducted across Medline, Embase, PubMed, and Cochrane Library databases.
• Inclusion of randomized controlled trials (RCTs) of ≥12 months duration, focusing on adult participants with BMI ≥25 kg/m².
• Data extraction and risk of bias assessment performed independently and in duplicate, with meta-analysis using RevMan 5.3.

Main Results:

• Twenty-three RCTs were included, with most exhibiting high or unclear risk of bias and interventions lasting 12 months.
• High-fat, low-carbohydrate (HFLC) diets demonstrated a modest reduction in fat mass compared to moderate macronutrient (MM) diets (MD, -2.88 kg).
• No significant differences in fat mass reduction were observed between MM diets and usual diets (UD), nor between HFLC and LFHC diets. Data on bone mineral density were scarce, with a potential benefit noted for high-protein diets.

Conclusions:

• High-fat, low-carbohydrate diets offer a modest benefit in reducing fat mass compared to moderate macronutrient diets.
• Dietary interventions showed no significant differences in other body composition parameters, and data on bone mineral density remain limited.
• Further high-quality, long-term randomized controlled trials are essential to clarify the impact of various diets on body composition and bone mineral density.