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Taking a break from dieting may improve weight loss

MedDietGreater weight and fat loss were achieved with intermittent energy reduction, the randomised controlled Matador Study trials at the University of Tasmania show.

In the findings, School of Health Sciences researchers showed in a randomised controlled trial, that taking a two-week break during dieting may improve weight loss.The study, funded by the National Health and Medical Research Council (NHMRC) of Australia, investigated the body's 'famine reaction' to continued dieting and its impact on weight loss in men with obesity.

During the study, two groups of participants took part in a 16-week diet which cut calorie intake by one third. One group maintained the diet continuously for 16 weeks while the other maintained the diet for two weeks, then broke from the diet for two weeks eating simply to keep their weight stable, and repeated this cycle for 30 weeks in total to ensure 16 weeks of dieting.

Those in the intermittent diet group not only lost more weight, but also gained less weight after the trial finished. The intermittent diet group maintained an average weight loss of 8 kg more than the continuous diet group, six months after the end of the diet.

Head of the University of Tasmania's School of Health Sciences, Professor Nuala Byrne, who led the study with a team of collaborators from Queensland University of Technology and the University of Sydney, said dieting altered a series of biological processes in the body, which led to slower weight loss, and possibly weight gain.

"When we reduce our energy (food) intake during dieting, resting metabolism decreases to a greater extent than expected; a phenomenon termed 'adaptive thermogenesis' — making weight loss harder to achieve," Byrne said. "This 'famine reaction', a survival mechanism which helped humans to survive as a species when food supply was inconsistent in millennia past, is now contributing to our growing waistlines when the food supply is readily available."

Byrne said while researchers in the past had shown that as dieting continued weight loss became more difficult, this latest MATADOR (Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound) study looked more closely at ways to lessen the famine response and improve weight loss success.

However, Byrne said while this two-week intermittent diet proved to be a more successful means of weight loss compared with continuous dieting, other popular diets which included cycles of several days of fasting and feasting were not any more effective that continuous dieting.

"There is a growing body of research which has shown that diets which use one to seven-day periods of complete or partial fasting alternated with ad libitum food intake, are not more effective for weight loss than conventional continuous dieting," she said.
"It seems that the 'breaks' from dieting we have used in this study may be critical to the success of this approach.

"While further investigations are needed around this intermittent dieting approach, findings from this study provide preliminary support for the model as a superior alternative to continuous dieting for weight loss."

Abstract
Background/Objectives: The MATADOR (Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound) study examined whether intermittent energy restriction (ER) improved weight loss efficiency compared with continuous ER and, if so, whether intermittent ER attenuated compensatory responses associated with ER.
Subjects/Methods: Fifty-one men with obesity were randomised to 16 weeks of either: (1) continuous (CON), or (2) intermittent (INT) ER completed as 8 × 2-week blocks of ER alternating with 7 × 2-week blocks of energy balance (30 weeks total). Forty-seven participants completed a 4-week baseline phase and commenced the intervention (CON: N=23, 39.4±6.8 years, 111.1±9.1 kg, 34.3±3.0 kg m−2; INT: N=24, 39.8±9.5 years, 110.2±13.8 kg, 34.1±4.0 kg m−2). During ER, energy intake was equivalent to 67% of weight maintenance requirements in both groups. Body weight, fat mass (FM), fat-free mass (FFM) and resting energy expenditure (REE) were measured throughout the study.
Results: For the N=19 CON and N=17 INT who completed the intervention per protocol, weight loss was greater for INT (14.1±5.6 vs 9.1±2.9 kg; P<0.001). INT had greater FM loss (12.3±4.8 vs 8.0±4.2 kg; P<0.01), but FFM loss was similar (INT: 1.8±1.6 vs CON: 1.2±2.5 kg; P=0.4). Mean weight change during the 7 × 2-week INT energy balance blocks was minimal (0.0±0.3 kg). While reduction in absolute REE did not differ between groups (INT: -502±481 vs CON: −624±557 kJ d−1; P=0.5), after adjusting for changes in body composition, it was significantly lower in INT (INT: −360±502 vs CON: −749±498 kJ d−1; P<0.05).
Conclusions: Greater weight and fat loss was achieved with intermittent ER. Interrupting ER with energy balance ‘rest periods’ may reduce compensatory metabolic responses and, in turn, improve weight loss efficiency.

Authors
N M Byrne, A Sainsbury, N A King, A P Hills, R E Wood

[link url="https://www.sciencedaily.com/releases/2017/09/170918222235.htm"]University of Tasmania material[/link]
[link url="http://www.nature.com/ijo/journal/vaop/ncurrent/full/ijo2017206a.html?foxtrotcallback=true"]International Journal of Obesity abstract[/link]

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