Role of Leucine on Muscle Preservation During Weight Loss in Older Men

BMI>=23 kg/m2, Overweight and Obese Adults

Overweight, Obese, Intermittent Fasting, Alternate Day Fasting, Protein, Leucine, Skeletal muscle, muscle, blood health, mood, appetite, food craving

Overweight and obesity are part of a global health epidemic. However, older adults trying to lose weight face a dual challenge: first, muscle mass and strength naturally decline at an accelerating rate with age; second, effective weight loss diets like alternate-day fasting (ADF) are typically accompanied by significant muscle loss. Together, these factors can increase the risk of developing sarcopenia, a muscle disease characterized by critical losses in muscle mass and strength, especially when overweight or obese older adults try to lose weight through dieting alone. While high protein diets have often been advocated as a muscle preserving strategy when losing weight, recently, high leucine intake has been promoted for its critical role in stimulating muscle protein synthesis (MPS) with lower overall protein consumption, potentially reducing calorie intake while maintaining muscle during weight loss. Nonetheless, the effects of body mass-scaled protein and leucine intakes on muscular outcomes during weight loss remain uncertain. This study examines the effects of body mass-scaled protein and leucine supplementation on body composition during four weeks of ADF in older men.

Participation in this study requires a total of 4 weeks of alternate day fasting (ADF) and 3 laboratory visits (sessions) spread over 5-6 weeks. All sessions are done in a fasted and rested state. Participants will complete 4 weeks of ADF alternating between ad libitum feeding days and fasting days consisting of a small midday meal of up to 600 kcal. Supplements will be provided to participants (3 servings on feeding days and 1 serving on fasting day). Prior to each session, participants are required to: * Abstain from any physical activity except activities of daily living for at least 48 hours. * Abstain from alcohol and caffeine for at least 24 hours. * Fast (i.e., do not eat or drink except plain water) overnight for 10 hours. In consideration of the fasting, these sessions will take place in the morning. To control for diurnal variation, the sessions will be timed such that the same measurements will be taken at approximately the same time of the day (+/- 1 hour difference). * Obtain a full night of sleep the night before. Session 1 * Read and sign consent form * Pre-screening: * Subject screening questionnaire * Global Physical Activity Questionnaire * Body mass * Height * Resting blood pressure and heart rate * Fasting blood glucose (via finger prick) Session 2 The 4-week alternate-day fasting programme will start within 14 days from session 1 * Collection of 4 weeks of supplements * Body mass * Height * Resting blood pressure and heart rate * Fasting blood glucose (via finger prick) * Waist and hip circumference measurements * Body composition using bioelectrical impedance analysis and dual-energy X-ray absorptiometry * Handgrip strength test * Gait speed test * Short physical performance battery * Complete questionnaires on food craving, mood, appetite, hunger, satiety, diet satisfaction, and cognitive function * Blood sample from forearm (35 ml) Session 3 28 days (4 weeks) after the start of alternate-day fasting • Same as session 2 except collection of supplements (not applicable)

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