Weighing the evidence... Diabetes Australia

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Weighing the evidence

Obesity is rapidly on the rise in Australia - but you can do something to stop this trend. Access up-to-date information on lifestyle intervention.

The AusDiab study estimated that in the year 2000, 52% of Australia women and 67% of Australia men were overweight (BMI > 25 kg/m2) or obese (BMI > 30 kg/m2) (source: 1).

The development of Type 2 diabetes is one of the most immediate outcomes of excess body fat, with overweight/obese individuals having up to three times the risk of developing the condition compared to their leaner counterparts (2,3).

A sustained reduction in weight (5-10% of initial body mass) can result in clinically relevant health benefits, including a reduction in blood pressure (4) and improved blood lipids (5). A more substantial weight loss of 15-20% in the first year post diagnosis of Type 2 diabetes can substantially reverse the risk of mortality associated with the condition (6).

How can sustained weight loss be achieved?

The aetiology of overweight/obesity is multifactorial, and includes the interaction of genetics, excess energy (kilojoule) intake, insufficient physical activity, and psychosocial issues (7).

To date, all successful long-term (five or more years) weight management programs have involved some form of lifestyle modification that either reduces an individuals energy intake (less kilojoules) or increases their energy expenditure (more physical activity) (8), creating a net energy deficit.

However, in many individuals, behavior modification, pharmacotherapy and/or surgery can be useful adjuncts to lifestyle modification (7). An energy deficit can be achieved through the restriction of any or all of the macronutrients: fat, carbohydrate, or protein. However, any changes that are made must be sustainable in the long-term, and must provide all essential nutrients in sufficient quantities to ensure health is not further compromised.

Because fat contains the most kilojoules per gram (twice that of carbohydrate and protein), restriction of an individuals fat intake is one of the most practical ways of producing an energy deficit. However, if the kilojoules from fat are replaced by an equivalent amount of energy from carbohydrate or protein, weight loss will not be achieved.

Low-fat high-carbohydrate diets or low-fat higher-protein diets will both decrease body fat in the short-term if energy intakes are low enough. However, there is no evidence to-date to support any beneficial effect of consuming a low-fat higher-protein diet in the long-term (7). Therefore, despite much debate in the popular media, the current evidence supports the use of a low-fat higher-carbohydrate eating plan that results in a net reduction of between 2000 and 4000 kilojoules (500-1000 Calories) per day as the most effective means of achieving long-term weight loss (7).

Regular weight-bearing activities such as walking, light jogging, dancing, etc… are most effective for long-term weight loss. Non-weight bearing activities such as swimming or cycling are also useful, particularly for individuals with limited mobility (7). In line with the National Physical Activity Guidelines (9), individuals should aim to do at least 30 minutes of physical activity, most days of the week.

Lastly, although successful weight management is ultimately the patients’ responsibility, their efforts can be supported by long-term contact with a range of health care professionals including medical practitioners, dietitians, diabetes educators, exercise physiologists, and/or psychologists (10).

References:

1. Diabesity and Associated Disorders in Australia 2000. The Australian Diabetes, Obesity and Lifestyle Study (AusDiab). International Diabetes Institute, Melbourne, 2001.
2. Carey VJ, Walters EE, Colditz, et al. Body fat distribution and the risk of non-insulin-dependent diabetes mellitus in women: the Nurses Health Study. Arch Intern Med. 2000; 160(14): 2117-28.
3. Chan JM, Rimm EB, Colditz GA, et al. Obesity, fat distribution and weight gain as risk factors for clinical diabetes in men. Diab Care. 1994; 17(9): 961-9.
4. Davis BR, Blauxfox MD, Oberman A, et al. Reduction in long-term antihypertensive medication requirements: effects of weight reduction by dietary intervention in overweight persons with mild hypertension, Arch Intern Med. 1993; 153(15): 1773-82.
5. Dattile AM and Kris-Etherton PM. Effects of weight reduction on blood lipids and lipoproteins: a meta-analysis. Am J Clin Nutr, 1992; 56(2): 320-8.
6. Lean ME, Powrie JK, Anderson AS and Garthwaite PH. Obesity, weight loss and prognosis in Type 2 diabetes. Diab Medicine. 1990; 7: 228-33.
7. National Health and Medical Research Council. Draft National Guidelines for Weight Control and Obesity Management in Adults. Commonwealth of Australia, 2002.
8. Poston W II, Foreyt J. Successful management of the obese patient. Am Fam Phys. 2000; 61(12): 3615-22.
9. Dept. Health and Aged Care. National physical activity guidelines for Australians. Canberra, 1999.
10. American Association of Clinical Endocrinologists & American College of Endocrinology. AACE/ACE position statement on the prevention, diagnosis and treatment of obesity. Endoc Prac. 1998; 4(5): 297-330.