Intermittent fasting: is it a valid treatment option for obesity and diabetes prevention?

Abstract

Background and aim Intermittent fasting interventions may have several advantages over daily caloric restriction among people with pre-diabetes. Intermittent fasting, due to the periods of ad libitum intake, is thought to improve metabolism, including glucose control, independent of reduced calorie intake and lead to longer term weight loss. The aims of this PROFAST sub-study was to (a) develop intermittent fasting support for the multi-ethnic NZ population (b) test whether Intermittent fasting improves glycemia and weight loss, in a pilot study among people with prediabetes. Methods 16 participants participated in an Intermittent fasting protocol, over a 12-week period, which required 5 days of ad libitum eating and 2 days of restricting calories to 600kcal/day for women and 650 kcal/day for men. All participants received dietary advice and education regarding fasting and support, at baseline and throughout the 12 weeks, including written information, fortnightly face-to-face, phone and/or email contact, a private Facebook group and helpful apps. Assessments at baseline included: DXA, anthropometric measures (weight, height, body mass index (BMI), waist, hip and neck circumference, and waist hip ratio (WHR), closed circuit indirect calorimetry, SF12, Mood and Eating questionnaire and a 7-day food diary. All participants were asked to keep a food diary for fasting days only and were contacted fortnightly, by the study dietitian, for dietary support, with the opportunity for further contact, if required. All formal assessments were repeated at 12 weeks, with the addition of a 12-week interview with the study dietitian, for qualitative data collection. Results 2 of the 16 participants withdrew from the study, at 12 weeks. Data from 14 participants were analysed. All had significant weight loss (mean values ranged from 96.3kg at baseline to 90.8kg at 12 weeks, p= 0.0001) and loss of total fat (mean values ranged from 43.8kg to 40.1kg at 12 weeks, p=0.001), visceral fat (2.04kg to 1.79kg p=0.007) and abdominal fat (4.55kg to 4.01kg p=0.0006). Participants lost an average of 23% of lean tissue mass (p= 0.01) and no change to bone mass. HbA1c was significantly reduced by 2.8mmol/mol, with a baseline and 12 week mean of 43.9 to 41.1 mmol/mol (p=0.001) in all participants except for 1, which stayed the same. Resting energy expenditure (REE) was reduced in most participants, but was consistent with the loss of fat free mass (FFM). Respiratory Quotient (RQ) was reduced from 0.81 to 0.76 (p= 0.013): RQ at 12 weeks was strongly correlated with weight loss (kg) (p = 0.005), but was not correlated with macronutrient intake. 11 of the 14 participants (78.6%) had good adherence with certain factors affecting ability to adhere, for example participants with family members fasting with them (n=3), lost the most amount of weight (p = 0.009). Conclusion Intermittent fasting (IF) results in significant weight loss and improved glucose control. IF may have benefits improving metabolic flexibility and increasing fat oxidation.