SEMINAR: Losing excess body weight or fat without losing strength or lean tissues
|Losing excess body weight or fat without losing strength or lean tissues : School of Human Sciences Seminar Series
While reducing excess body weight or fat is important for certain athletes and for the treatment of overweight and obesity, it is essential that weight loss interventions do not result in losses of physical strength or lean tissues such as muscle and bone, any of which could impair physical abilities and increase the risk of structural diseases such as sarcopenia or osteoporosis.
A dietary intervention showing potential for reducing body weight and fat without excessive loss of lean tissues is a novel form of intermittent energy restriction (IER) entailing repeated cycles on a moderately kilojoule-restricted diet for 2-4 weeks, interspersed with 2-week periods of energy balance, where kilojoule intake is matched to energy requirements and weight is maintained. In a randomized controlled trial of 51 men with obesity, this form of IER significantly improved weight and fat loss compared to continuous energy restriction (CER): weight loss 14.1 ± 5.6 versus 9.1 ± 2.9 kg; fat loss 12.3 ± 4.8 versus 8.0 ± 4.2 kg; means ± SD, P<0.01 for both comparisons), with no difference in loss of fat free mass (1.8 ± 1.6 versus 1.2 ± 2.5 kg; P = 0.4)1.
Another dietary intervention with potential for body weight and fat loss without excessive loss of strength or lean tissues in people with overweight or obesity is paradoxically fast weight loss, achieved via total meal replacement diets. The TEMPO Diet Trial (ACTRN12612000651886) has shown that at 1 year after commencement of a diet involving either fast or slow weight loss in postmenopausal women with obesity, there was no difference between diets with respect to muscle (handgrip) strength, fat free mass or bone mineral density, despite the fact that women on the fast diet lost almost twice as much weight and fat as women on the slow diet (16.9 ± 7.1 versus 9.7 ± 7.5% of body weight, and 11.1 ± 5.6 versus 6.1 ± 5.5 kg of fat mass; P<0.001 and P<0.05, respectively).
In light of the greater weight and fat loss achieved using IER as opposed to CER, as well as the lack of apparent deleterious effect of fast versus slow weight loss on muscle strength or lean mass despite markedly greater weight and fat loss, an NHMRC-funded randomised controlled trial, commencing 2018, aims to determine whether greater weight and fat loss without greater loss of strength or lean tissues can be achieved via intermittent use of fast weight loss in adults with overweight or obesity. If yes, then determining the mechanisms for any potential advantage of IER over CER (e.g. via reduced energy efficiency as a result of switching between carbohydrate and lipid or ketone oxidation in skeletal muscle) could enable IER interventions to be further improved. Moreover, future work to determine whether/how physical activity improves weight loss outcomes from IER (e.g. via attenuation of the drive to eat as a result of greater lean mass retention) could provide motivating reasons for people with overweight or obesity to exercise during weight loss interventions.
1. Byrne NM, Sainsbury A, King NA, Hills AP, Wood RE Intermittent energy restriction improves weight loss efficiency in obese men the MATADOR study. International Journal of Obesity 2017 doi: 10.1038/ijo.2017.206 [Epub ahead of print]
With a Bachelor of Science from the University of Western Australia and a PhD from the University of Geneva, Switzerland, Professor Amanda Salis (publishing as Sainsbury) leads full-time research into dietary treatments for overweight and obesity at the University of Sydneys Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders in the Charles Perkins Centre. Her translational research into hypothalamic control of appetite, eating behavior, energy expenditure, body weight and body composition spans transgenic mice, adults with overweight or obesity, as well as adult athletes. Her randomized controlled trials comparing long-term effects of fast versus slow weight loss using intermittent versus continuous energy restriction are funded by a Senior Research Fellowship and Project Grants from the National Health and Medical Research Council (NHMRC). She is the author of two books about adult weight management that are available internationally in three languages and are used by consumers, community health centres / gyms, and by healthcare professionals (e.g. general practitioners, physiotherapists, dieticians, diabetes educators and psychologists).
Amanda Salis, NHMRC Senior Research Fellow, The Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders The University of Sydney
Seminar room 1.81 (first floor) Anatomy building, The University of Western Australia
: 6488 3313
Tue, 27 Feb 2018 13:00
Tue, 27 Feb 2018 14:00
Deborah Hull <[email protected]>
Fri, 23 Feb 2018 09:25
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