A Conversation with Alisha Wade, MBBS, DPhil
Obesity is most commonly defined using the body mass index (BMI), in which weight in kilograms is divided by height in meters squared. An individual is said to have obesity when the BMI is over 30 kg/m2.
Obesity is associated with a higher risk of several conditions. These include type 2 diabetes mellitus, hypertension, abnormal cholesterol levels, coronary heart disease, heart failure, stroke and several cancers, including endometrial, colon, and kidney cancers. Obesity is also associated with osteoarthritis, gout, infertility and depression. Overall, over 200 health conditions are thought to be associated with obesity. The risks of many of these conditions improve after weight loss.
Approximately 40-70% of BMI in adults is genetic, but obesity is a complex disease that occurs due to the interaction of several genetic changes that influence weight gain with environmental factors such as reduced physical activity and consuming more calorie-dense foods. While the FTO gene has been identified as strongly associated with obesity, in most people with obesity, there is no single gene responsible and genetic testing is not clinically useful.
There are rare forms of obesity which are caused by single genes (monogenic obesity). Monogenic obesity is associated with severe weight gain early in life and may be due to genetic mutations that result in excess eating or slow metabolism. The genetic mutations that result in monogenic obesity are usually associated with other clinical features such as in Prader-Willi and Bardet-Biedl syndromes. In other genetic disorders, such as those of leptin, obesity is the isolated or predominant feature.
Obesity treatment is geared toward treating or reducing the risk of obesity-related complications. Weight loss of as little as 5% of body weight may result in health benefits, even though it may not give the desired cosmetic effect.
All obesity treatments should be based on sustainable lifestyle modification which includes caloric reduction and increased physical activity. Even in ideal circumstances, lifestyle modification usually achieves weight loss of 5-7%. Additional weight loss requires the use of medication which can produce a weight loss of approximately 10%, although newer agents may produce weight loss of 20-25%.
Several devices, including gastric bands, balloons which are placed in the stomach and absorbent gels which are taken daily may be used in patients who cannot tolerate medications, who cannot or prefer not to have bariatric surgery or who are awaiting bariatric surgery. Bariatric surgery can achieve the most substantial weight loss- up to 40%. Patients with obesity should speak to their doctor about which management approach is best for them.
Obesity is a major public health challenge and considerable research is underway to improve our understanding of it. Some key questions being investigated include:
Lifestyle modification is the bedrock of obesity therapy and has to include both fewer calories and increased activity. While seemingly minor weight loss of 5% may not achieve the desired cosmetic effect, it can result in improved health outcomes.
Alisha Wade, MBBS, DPhil is a Reader and Clinician scientist in the MRC/Wits Rural Public Health and Health Transitions Research Unit in the School of Public Health at the University of the Witwatersrand in Johannesburg, South Africa and an endocrinologist at the Wits Donald Gordon Medical Center, also in Johannesburg.. Her research is focused on chronic diseases in developing countries.
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