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Weighing In on the Diet VS Physical Activity Debate

Photo: vitals.lifehacker.com

A recent editorial published in the British Journal of Sports Medicine ("It is time to bust the myth of physical inactivity and obesity: you cannot outrun a bad diet") has been the topic of online buzz in recent weeks, having generated discussions on MashableYahoo and The Straits Times Forum.

While acknowledging that regular exercise does have multiple health benefits such as reducing the risk of developing numerous health conditions and diseases, the article claims that “physical activity does not actually promote weight loss”. The reason behind this? As alleged by the authors – obesity is caused solely by poor consumer dietary habits, egged on by misleading messages purported by the food industry.

Indeed, to control and manage obesity, as the article rightly acknowledges, we cannot rely on physical activity alone without changes in diet.However, contrary to the article’s claims, regular physical activity together with a calorie-controlled diet does, in fact, contribute to long-term weight loss and control – and this has been supported by a wealth of scientific evidence, says Associate Professor Rob van Dam, a nutritional epidemiologist at the Saw Swee Hock School of Public Health who has conducted extensive research on dietary intake and its effects on health status. In fact, readers who do not know better could misinterpret the article as evidence that physical activity is not important for one’s health.

“As part of a study at the Harvard T.H Chan School of Public Health, we reviewed the effects of different interventions on weight loss and found that diet-plus-exercise interventions have provided consistently and significantly greater weight loss than diet-only interventions,” explains A/Prof van Dam. 

Weight loss: it takes a balance of physical activity and good dietary habits to achieve it. 

Photo: James Wojcik

And research has also yielded evidence of other health benefits when it comes to regular physical activity. “In another study, we followed more than 77,000 middle-aged women over 24 years and found that healthy lifestyle behaviours was linked to a lower risk of premature death. Around 55% of deaths, 72% of cardiovascular deaths and 44% of cancer deaths could have been avoided if the women did not smoke, had a healthy diet, regular physical activity, and avoided becoming overweight. Hence, it was found that physical activity had substantially contributed to longevity of the women independent of other lifestyle factors,” adds A/Prof van Dam. 

Closer to home, another study conducted at the NUS Saw Swee Hock School of Public Health has supported this, linking the importance of both dietary factors and physical activity to preventing insulin resistance, a major underlying cause of diabetes in the Singapore population.

Lastly, another problematic point about the article are the authors’ seemingly interchangeable usage of the terms “exercise” and “physical activity”, which could lead to further misconceptions among readers. In fact, the two are decidedly different. While “exercise” is restricted to an intentional, structured activity i.e. jogging or swimming, “physical activity” encompasses exercises, but goes beyond to also include physical activities as part of daily living, such as walking to school/work or climbing the stairs, explains Dr Falk Mueller-Riemenschneider from the Saw Swee Hock School of Public Health, whose research specialises in physical activity and obesity prevention.   

There is no singular reason behind obesity and the fact that diet plays a key role does not mean that physical activity is not important. In short, the main message that readers should take away is that a healthy diet alongside an active lifestyle remain key components to ageing healthily and gracefully. 


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