Fatness vs Fitness

Whilst some aspects of the diet versus exercise comparison are becoming clearer, much uncertainty remains.
Popular questions asked include:

If I am overweight can I get away with it as long as I exercise?

For women
A new US study published in JAMA Sept 8 2004 (vol 292, no. 10, pp 1188-94) showed that being overweight is a better predictor in women of the risk of developing diabetes than is fitness. A total of 37,878 women were studied free of diabetes, heart disease or cancer at onset and followed up after 7 years. Both activity level and BMI had an impact on the risk of developing diabetes, but BMI had a larger effect.

So this study suggests that exercise alone is not enough in women to prevent diabetes and that fitness does not appear to cancel out the potential 'harm' of being over-fat.

For men
25,000 men were followed-up for 12 years to determine whether fitness or fatness is the main factor associated with death and/or disease. These men attended the Cooper Institute for Aerobics Research in Dallas Texas. The Director, Dr Steve Blair had access to the records of thousands of people who came to the institute each year to be health tested. These men were given a comprehensive medical examination including body fat and physical fitness (e.g treadmill time to exhaustion) and were followed up over many years to see who develops what diseases, and associated these with the baseline measure of fitness. The men were grouped into 3 different tertiles (thirds) according to their baseline fitness. The study showed that irrespective of whether a person is overweight or normal weight, is a smoker or non-smoker, has high or normal blood pressure, or has a history of heart problems in the family, the risk of death and disease is much lower in those who are physically fit, than those who are unfit. Estimates of the odds of dying of any cause show that these are almost twice as high in the unfit, lean individual than they are in the fit, overweight. For diabetes risk, which has typically been thought to be greater in the overweight, the risk ratios were up to 4 times lower in men with higher fitness levels irrespective of weight, age, parental history and even increased blood sugars.

Unlike the study above, this study suggests that if you are an overweight male, becoming fit through exercise can potentially cancel out the potential 'harm' of being over-fat.

Brodney S, Blair SN, Chong Do Lee. Is it possible to be overweight or obese and fit and healthy? In Bouchard C (ed). Physical activity and obesity, Human Kinetics, Champaign 111., 2000. J of Eating Disorders 2000; 28: 215-220.

Will I lose weight if I concentrate on exercise and not worry about what I eat?

For men
An Australian trial on overweight men found that energy restriction alone reduced body and fat mass, but vigorous exercise did not, neither on its own nor when added to diet (Metabolism Jan 2003, vol 52 (1), pp 107-15). So this study suggests that exercise alone will not lead to fat loss. However, there is reasonable evidence that physical activity reduces abdominal obesity and increases the likelihood of maintaining weight loss long-term (Cardiol Clin. 2001 Aug;19(3):459-70; Int J Obes Relat Metab Disord 1994 Jan;18(1):35-40; Sports Med. 2004;34(6):371-418; J Nutr. 2002 Dec;132(12):3826S-3829S.)

For men and women
A new study published in the January 12, 2004 Archives of Internal Medicine.finds that physical activity in previously sedentary adults led to weight loss even when they were not dieting and had been encouraged not to lose weight. Middle-aged, overweight men and women were divided into four groups of about 30 and studied for three years. Groups were instructed to get low amount of exercise at moderate intensity, low amount at vigorous intensity, high amount at vigorous intensity, or remain sedentary. Controls gained weight and body fat while all three exercise groups lost both weight and fat. The participants took two to three months to work up to their assigned level of activity. The lowest amount of activity was equal to walking for 30 minutes daily. This led to a 4.4 pound (2.0 kg) weight loss, which is not much, but was statistically significant. Given that the participants did not diet and were encouraged to maintain weight, this is a very positive result. Both longer duration and greater intensity of exercise led to more weight and fat loss. This is the first controlled study to report on this.

What do we make of these studies?
Uncertainty still seems to prevail in the field of obesity.
Until the studies are conclusive HEC's nutrition experts suggest for both men and women that you combine moderate daily exercise with healthy eating and try to lose a few kilograms if you are overweight.

Last Updated: October 2004