Comparison of Intermittent Fasting Versus Caloric Restriction in Obese Subjects: A Two Year Follow-Up

Area of Science:

• Metabolic Health
• Endocrinology
• Nutritional Science

Background:

• Caloric restriction (CR) is known to increase lifespan and impact health.
• Nutritional habits, sleep patterns, and meal frequency significantly affect human health.
• Ramadan fasting provides a unique model for studying intermittent fasting (IF) in humans.

Purpose of the Study:

• To investigate the effects of intermittent fasting (IF) versus caloric restriction (CR) on the growth hormone (GH)/Insulin-like Growth Factor (IGF)-1 axis and insulin resistance.
• To compare the long-term metabolic impacts of IF and CR in non-diabetic obese subjects.

Main Methods:

• A single-arm interventional study involving 23 obese female subjects (BMI 29-39).
• A 24-month follow-up including periods of CR (low-calorie diet) and IF (15-hour daily fast without calorie restriction).
• Monitoring of BMI, blood glucose, insulin, TSH, GH, HbA1c, IGF-1, Homa-IR, and urinary acetoacetate levels.

Main Results:

• CR led to significant monthly weight loss (1250g), while IF resulted in less weight loss (473g).
• Both CR and IF decreased BMI, glucose, HbA1c, insulin, Homa-IR, and TSH levels.
• IF increased urinary acetoacetate, indicating lipid catabolism, and metabolic rhythm changes were observed.

Conclusions:

• CR positively affects metabolic parameters, beneficial for pre-diabetic and insulin-resistant individuals.
• IF, even without calorie restriction, can enhance health and cellular resistance through different signaling pathways and circulating ketones.
• Observed changes during IF are likely linked to altered eating and sleeping patterns, affecting metabolic rhythm.