Brian Corley 1,2, Christina Khouri1, Lorene Theaude1, Philippa Hawke1, Rosemary Hall1,2, Mark Weatherall1,2, and Jeremy Krebs1,2

1University of Otago, Wellington, New Zealand2Capital and Coast District Health Board, Wellington, New Zealand

Background: Overweight and obesity now affects two in three New Zealand adults.1 Of the many complications of obesity type 2 diabetes mellitus (T2DM) is one of the most challenging. It is associated with significant morbidity, cost and reduced life expectancy. The global prevalence of T2DM has quadrupled in the last 36 years2. Dietary calorie restriction induces weight loss for the treatment of obesity and reverses dysglycaemia in T2DM in proportion to the degree of calorie restriction.3 There has been much interest in whether the timing of calorie restriction provides additional benefit to such a diet. One possible mechanism is an attenuation in the drop in basal metabolic rate commonly seen within a few weeks of starting an energy restricted diet. This reduction in basal metabolic rate is known as adaptive thermogenesis.4 Adaptive thermogenesis reduces the calorie requirements of a fasting individual below that expected for weight, thus reducing weight loss during a low‐calorie diet. An attenuation in adaptive thermogenesis with intermittent fasting may promote more effective weight loss during dietary energy restriction.

Aims: To determine if intermittent fasting produces less adaptive thermogenesis compared with continuous daily restriction during a six‐week dietary intervention.

Methods: We conducted a randomized controlled trial in obese men of 79% daily restriction versus an energy matched intermittent fast consisting of two days of 25% restriction and 5 days of isocaloric intake per week over six weeks. Body composition by dual energy x‐ray absorptiometry, resting energy expenditure by indirect calorimetry and anthropometry were measured at baseline, three weeks and six weeks. Secondary outcomes were change in glycated haemoglobin, blood pressure, fasting lipids, leptin, ghrelin, adiponectin and thyroid function tests. A general linear mixed model was used for the primary outcome. Analysis of co‐variance was used for all secondary outcome variables.

Results: Thirty‐two men completed the diet intervention and lost approximately 1 kg per week. Intermittent energy restriction did not alter weight loss or attenuate adaptive thermogenesis. There was a greater fat mass reduction with intermittent fasting.

Conclusion: Intermittent fasting does not attenuate adaptive thermogenesis. A generalized linear mixed model approach is suggested for studies of RCT's examining adaptive thermogenesis.

References

1. Ministry of Health. New Zealand Health Survey: Annual update of key findings 2015/16. Wellington: Ministry of Health; 2016.

2. World Health Organisation. Global Report on Diabetes. World Health Organisation; 2016.

3. Lean ME, Leslie WS, Barnes AC, Brosnahan N, Thom G, McCombie L, et al. Primary care‐led weight management for remission of type 2 diabetes (DiRECT): an open‐label, cluster‐randomised trial. Lancet. 2017.

4. Muller MJ, Enderle J, Bosy‐Westphal A. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. Curr Obes Rep. 2016;5(4):413‐23.