Summary of main points.
- Fat is oxidised under aerobic conditions.
- Optimal fat utilisation in unfit people occurs at a lower exercise intensity compared to fit people.
- Fat utilisation also increases proportionately with exercise duration.
- Hence, low-moderate intensity, long duration activity is most appropriate for fat loss in those likely to require this most.
- Increasing both ‘planned’ and ‘incidental’ physical activity is important in any fat loss program.
- In general, weight-bearing physical activities are best for fat loss, except perhaps in the initial stages or for the very obese.
Ask anyone what they think is the best way to lose fat and the two sure answers are ‘diet’ and ‘exercise’. And while diet—or at least a change in eating patterns—is well accepted at the scientific level, it is surprising how little scientific support there is for exercise. Most scientists working in the area will agree that some form of exercise (or perhaps more appropriately, physical activity) built into an individual’s lifestyle, is probably more important than food restriction for long term prevention of fat gain, but there is much less agreement on the benefits of exercise in initial fat loss.
Some researchers have pointed to the relatively small levels of energy expenditure involved in significant levels of exercise. It is typical to find popular diet programs, for example, pointing out mat walking a kilometre uses only around 100kcal, which is quickly negated by a glass of beer or small piece of cake. However, the benefits claimed for exercise by its exponents are greater than this. Some forms of exercise have been claimed to increase long term metabolic rate (although this remains controversial) and increase fat oxidation. In addition, exercise is often claimed to be much more psychologically pleasurable than restrictive dieting.
One of the problems in assessing the benefits of exercise in fiat loss has been the large individual differences in response to a given exercise load, and the many different types of physical activities that have been used in scientific research. The effect of a certain type of exercise in one group of people, such as young women, doesn’t necessarily mean that the same type, intensity and duration of exercise will have the same effect on another group, e.g. fat men.
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