Australasian Science: Australia's authority on science since 1938

Can You Outrun an Unhealthy Diet?

By Australian Science Media Centre

An editorial in the British Journal of Sports Medicine has blamed excess sugar and carbohydrates, and not a lack of exercise, behind the surge in obesity.

“It is a complete myth that sugar and carbohydrate alone are solely responsible for obesity. Australians eat over 30% of excess kilojoules from indulgence foods. Some may be high in sugar and carbohydrate, but many may also be high in fat and salt.

“Eating for good health and well-being will not be achieved by focussing on avoidance of one nutrient. The failure of low-fat foods will be repeated with low sugar and carbohydrate foods unless we focus on balanced nutrition. Exercise has many benefits, but particularly for weight loss maintenance rather than weight loss.”

Professor Manny Noakes is the Research Director for Nutrition and Health at CSIRO.


“The authors correctly highlight that regular exercise participation has many associated benefits that include reducing the risk of developing cardiovascular disease, Type 2 diabetes, dementia and some cancers. For these and a growing list of other reasons it is, and should continue to be, strongly endorsed. Nevertheless, as a tool for actually reducing bodyweight exercise is a reasonably inefficient method. Rather, for most people the key mediator of weight loss is caloric intake.

“The role of exercise in prevention of weight gain may perhaps be more substantial; one of the most common characteristics of people that have maintained a weight loss long-term is that they participate in regular physical activity. However, at a population level, minimising excess calorie intake is certainly a key consideration for prevention of obesity...

“There is a useful online tool by the NIH that can be used to reasonably predict individual weight changes in response to diet and exercise interventions” (

Dr Tom Wycherley is a Postdoctoral Research Fellow in the School of Population Health at the University of South Australia


“This exciting new research is further evidence of the significant role highly processed food plays in our battle with obesity... By showing that you can’t outrun a bad diet, this research flies in the face of food giants such as Coca Cola who are positioning themselves as part of the solution, telling consumers that managing weight is all about getting the energy balance right.

“We won’t solve our obesity problem with physical activity alone. We also won’t solve the issue by simply telling people what to do.

“To bring about change in our diets and really address our weight problem we need a comprehensive approach involving all levels of government and community.

“We need strong policies, such as restricting junk food marketing to children, regulating the quality and availability of food in school settings, taxing sugar-sweetened beverages, mass media campaigns, and placing the health stars on the front of packaging among others.”

Jane Martin is the Executive Manager of the Obesity Policy Coalition (OPC) and of alcohol and obesity policy at Cancer Council Victoria.


“This paper is not based on new research. It is an opinion piece published in a lowly journal. The authors are renowned for their unconventional views.

“The paper appears to be made-for-public relations, with the usual overstatement and demonisation of the food industry. But the arguments are poorly developed and misleading. For example, it is argued that the message to maintain a healthy weight through calorie control is a ‘false impression rooted in the Food Industry’s Public Relations machinery’. Rather, it’s the position advocated by all reputable nutrition and obesity organisations in the world.

“Some of the claims in the paper are simply wrong. For example, it is claimed that sugar calories promote hunger and fat calories promote fullness. However, studies directly comparing the effects of sugars and fats on satiety find there is little difference between the two. Protein is more satiating than both...

“I don’t understand why these authors would attempt to undermine recommendations for increased physical activity from an expert group. Both diet and exercise are important – it’s not a matter of one or the other.”

Bill Shrapnel is a Dietitian and Nutritionist and runs a website called the Sceptical Nutritionist. He is a member of the Sugar Research Advisory Service.


“I agree entirely that you ‘cannot outrun a bad diet’ but it is essential that we don’t turn Australians away from exercise and activity... Exercise may not be a route to weight loss in the short term, but it does have an important role in preventing weight gain and maintaining weight loss. Then, as the authors point out, there are numerous other health benefits to being more active. The bottom line is that, even in the absence of weight loss, being metabolically fit through regular exercise is essential for a well-functioning body...

“I do think we need more careful advice given to distinguish athletes from the everyday exerciser or ‘weekend warrior’. I agree with the authors that the legitimisation of certain products, including sports drinks, by their endorsements and associations with sport, needs to stop...

“Finally yes let’s make healthy the easy choice! How we do that is the question. Pointing the finger of blame at sugar, or carbs in general, and then replacing with a myriad of highly processed low carb products only repeats the mistakes of the past.”

Dr Joanna McMillan is a nutritionist, accredited practising dietitian and sports dietitian.