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Calorie restriction or exercise programmes?

School Of Nutrition Posted Nov 03, 2014 Future Fit Training

Diet and exercise are frequently cited methods for both men and women attempting weight loss and can be difficult to assess the two methods vigorously.

Calorie restriction or exercise programmes?

Most day to day weight-loss programmes and exercise routines found in modern day Women’s and Men’s magazines are experimental and lack the validation through scientific research that is demanded when prescribing treatment for medicinal practices.

There is an on-going debate within the scientific community on the independent and combined effects that dieting and/or increased physical activity has on weight loss and metabolic risk factors such as body composition and fat distribution.

First let’s consider the effects of diet (calorie restriction).  As common sense suggests, if you want to lose weight you take on less energy to tip the energy equation into deficit and lose the weight through restriction. This approach is widely supported by scientific research in the field (7,8).  A large number of studies have also shown that the most important factor when considering weight loss (compared to diet/exercise mixed regimes, exercise alone) is calorie intake (4, 6). Another good reason why focusing on calorie intake may be important is everyday behaviour. When we consider energy intake and everyday practicalities, the time is takes to tip the balance of the equation is heavily on the side of food.

A 100g chocolate bar can easily be eaten in two minutes. To burn off the equivalent amount of energy, the average person would have to run 8 Km. The amount of energy in that bar – 2,200 kJ or 500 calories – would be enough to fuel the body of a sedentary office worker for around five hours with no other food needed. So in everyday life small consistent changes in calorie restriction can produce significant outcomes. Making some concerted changes to the ‘input’ side of the energy balance equation can reap large benefits for weight loss.

Of course there are a whole range of other factors that we need to be mindful of and take into consideration when discussing the health repercussions of obesity. A large number of well-respected studies have also found that the inability of caloric restriction alone to alter the distribution of body fat suggests that individuals are genetically or epigenetically programmed for fat storage in a particular pattern and that this programing cannot be easily overcome by weight loss (2, 8).  It seems that when we try to holistically treat obesity and its related comorbidities we need to focus on more than just weigh loss. This is where the added benefits of exercise come in.

As well as its role in energy balance, exercise can also yield health benefits independent of changes in body weight such as improvements in glucose tolerance and aerobic fitness (1) A low level of aerobic fitness has been identified as a stronger predictor of cardiovascular disease mortality than other risk factors including body fatness (3). Improved mitochondrial function and muscle oxidative capacity are believed to be important adaptations of exercise that link aerobic fitness to cardiovascular and metabolic disease (5). So it’s possible that someone can exercise regularly, not lose any weight yet still improve a host of obesity-related risk factors.  
The question may not be “What is the best way to lose weight?” but rather “What are the specific endpoint benefits we are aiming for?” We can then begin to realise that both diet restriction (through a well-balanced nutritionally sound diet) and an appropriate exercise programme are needed to combat the effects of the obese condition. In fact, studies have found that subjects are more likely to continue the ‘diet’ or ‘exercise ‘programmes if there are also on the other programme in parallel.

You can learn more about the effects of foods on our interactive online Nutrition and Weight Management course here. 


1. Barlow, C.E., Kohl 3rd, H.W., Gibbons, L.W., Blair, S.N. 1995 Physical fitness, mortality and obesity. Int J Obes Relat Metab Disord 19(Suppl 4):S41–44

2. Bouchard C, Tremblay, A. Genetic influences on the response of body fat and fat distribution to positive and negative energy balances in human identical twins. J Nutr. 1997;127:943S–947S

3. Kavanagh, T., Mertens, D.J., Hamm, L.F., Beyene, J., Kennedy, J., Corey, P., Shephard, R.J. 2003 Peak oxygen intake and cardiac mortality in women referred for cardiac rehabilitation. J Am Coll Cardiol 42:2139–2143

4. Lee, C.D., Blair, S.N., Jackson, A.S. 1999 Cardiorespiratory fitness, body composition, and all-cause and cardiovascular disease mortality in men. Am J Clin Nutr 69:373–380

5. Kavanagh, T., Mertens, D.J., Hamm, L.F., Beyene, J., Kennedy, J., Corey, P., Shephard, R.J. 2002 Prediction of long-term prognosis in 12,169 men referred for cardiac rehabilitation. Circulation 106:666–671

6. Myers, J., Prakash, M., Froelicher, V., Do, D., Partington, S., Atwood, J.E. 2002 Exercise capacity and mortality among men referred for exercise testing. N Engl J Med 346:793–801

7. Ross R, Dagnone, D., Jones, P.J., Smith, H., Paddags, A., Hudson, R., Janssen, I. 2000 Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men. A randomized, controlled trial. Ann Intern Med 133:92–103

8. Slentz, C.A., Duscha, B.D., Johnson, J.L., Ketchum, K., Aiken, L.B., Samsa, G.P., Houmard, J.A., Bales, C.W., Kraus, W.E. 2004 Effects of the amount of exercise on body weight, body composition, and measures of central obesity: STRRIDE—a randomized controlled study. Arch Intern Med 164:31–39

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