Lifestyle intervention strategies for type 2 diabetes management.
Date
2011
Authors
Wycherley, Thomas Philip
Editors
Advisors
Brinkworth, Grant David
Clifton, Peter Marshall
Noakes, Manila
Clifton, Peter Marshall
Noakes, Manila
Journal Title
Journal ISSN
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Thesis
Citation
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Abstract
In parallel with the world wide increase in obesity there has been a dramatic rise in the prevalence of type 2 diabetes (T2DM) which is associated with a number of micro- and macro-vascular complications and increases the risk of coronary heart disease. Lifestyle intervention incorporating a hypocaloric weight loss diet and exercise training is currently recommended as the cornerstone of diabetes management and has been demonstrated to improve glycemic control and reduce cardiovascular disease (CVD) risk factors in individuals with T2DM. Previous research suggests that manipulating the dietary macronutrient composition may enhance the weight loss and improve the health status in patients undertaking a hypocaloric, weight-reducing diet. Within a low fat caloric restricted diet replacing a portion of carbohydrate with protein has been demonstrated to provide beneficial effects for weight loss, body composition, and cardiometabolic risk outcomes in overweight and obese individuals including patients with T2DM. Moreover combining a high protein, low fat hypocaloric diet with exercise training may provide additive benefits, however the efficacy of this strategy in patients with T2DM who may achieve the greatest benefits has been largely unexplored. The first study in this thesis was a randomised-controlled clinical study which investigated the effects of a high protein, low fat hypocaloric diet combined with exercise training compared to an isocaloric high protein, low fat diet without exercise training or an isocaloric standard protein, low fat diet with or without exercise training on weight loss, body composition and cardiometabolic risk markers in overweight and obese patients with T2DM. The results showed that compared to caloric restriction alone participation in exercise training during caloric restriction produced greater reductions in body weight and total body fat mass (FM) and increases in muscular strength. Additionally, replacement of some carbohydrate with protein further magnified these effects resulting in participants who consumed the high protein diet and participated in resistance exercise training experiencing the greatest reductions in weight, total body FM, abdominal FM and insulin levels. All treatments had similar improvements in glycemic control and CVD risk factors. These results suggest a lifestyle modification program that combines a calorie restricted high protein diet and exercise training appears to be a preferred treatment strategy in overweight/obese patients with T2DM. A separate line of evidence suggests manipulating the timing of protein intake in relation to exercise training (consuming protein adjacent to exercise training compared to a delayed intake) stimulates greater muscle protein synthesis and hypertrophy. This strategy may therefore promote greater muscle tissue retention and improvements in body composition during calorie-restricted induced weight loss. This hypothesis was tested in the second study in this thesis. However, this study showed in overweight and obese patients with T2DM undertaking a 16 week hypocaloric high protein, low fat diet plus exercise training lifestyle intervention program, that altering the timing of protein ingestion relative to exercise (by consuming a 21g protein supplement immediately before exercise compared to delaying ingestion 2 hours post-exercise) provided no additional benefit to weight loss and changes in body composition or cardiometabolic risk. The sustainability of the benefits obtained from intensive short-term research-based lifestyle intervention programs which incorporate an energy restricted diet and exercise is often poor, with a rebound frequently occurring following the cessation of the intensive support. The final study in this thesis followed up participants 1-year after the commencement of a 16-week research-based intensive lifestyle (diet and exercise) intervention program and reported factors identified by those participants as enhancing or impeding post-intervention program sustainability. Participants identified multiple reasons for the discontinuation of program components including; a desire for increased diet variety, a desire for increased portion size, limited access to appropriate exercise programs and facilities, the cost of gym membership and the withdrawal of professionals to motivate them. The main factors identified that would have facilitated continuation included having continued supervision or having to report to someone, having regular recorded weight checks and diet visits and access to affordable and appropriate exercise facilities. The findings of this thesis provide information that can be used by health professionals and policy makers for the development of evidence based recommendations and programs for the management of T2DM through diet and exercise based lifestyle intervention.
School/Discipline
School of Medical Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Medical Sciences, 2011
Provenance
Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.