Physical Activity

Physical activity is an important factor in the regulation of human energy metabolism. In terms of weight management the most important role of physical activity appears to be in the prevention of weight gain/regain. In other words, the benefits achieved by a moderate (30 min/day) level of physical activity on weight loss over and above that achieved by dietary restriction is modest, but in the case of maintaining a weight loss the inclusion of physical activity appears crucial.


Considering the laws of thermodynamics, this observation is not surprising. For example, a 1000 kcal/day reduction in energy intake produces a deficit of 7000 kcal/week that should produce a weight loss of 1 kg. Five hours of brisk walking  per week would expend approximately 1500 kcal that would produce a weight loss of only 0.2 kg.36 Expending 1500 kcal/week however is very important from the perspective of being able to maintain any weight lost. Several studies have demonstrated improvements in weight maintenance with the inclusion of physical activity.37, 38 This is an extremely important finding, given the poor success rate for the long-term maintenance of weight lost.

The benefits of physical activity in weight management should not focus on the outcome of weight loss or weight maintenance alone. In fact, physical activity should be strongly recommended primarily because of its effect on reducing disease risk and for the physical and psychological benefits that are associated with an improved level of fitness.39 Several studies have reported that being physically inactive is a strong independent risk for all cause mortality, and this risk is comparable to hypertension, hyperlipidaemia and smoking.40

Physical activity helps to:

  • Lower blood pressure
  • Reduce blood lipids
  • Improve glucose tolerance
  • Improve insulin sensitivity

In addition resistance training has been shown to preserve lean body mass.41 It has also been suggested that physical activity may aid dietary compliance, possibly by influencing appetite.42