Why fat people are fat
SIR: How right Dr Dalrymple is (December issue) when he promotes exercise as the first measure for those who are carrying too much embonpoint.
Everyone benefits from getting fitter, and the fitness element does neutralise some of the ill effects of the fatness. However, this is easier said than done.
Being overweight (with a BMI between 25 and 30) is no great threat, with only slight increases in morbidity and mortality compared with those of normal weight. Overweight individuals do gain from exercising more. As Dr D says, they probably won’t lose much weight, but they will live longer.
Being obese (BMI over 30), however, does matter, becoming exponentially more dangerous as BMI rises. The obese would be wise to lose weight if they can, particularly if they are diabetic – but it is extremely difficult. The best approach is both to diet and to exercise.
Exercise on its own needs to be hard, the equivalent of running 15 miles a week or more. Exercise is not readily adopted by the obese, which is why most of the obese are obese. As a result, only about four per cent of obese people can be classed as fat and fit.
A big problem is self-deception due to so-called social-desirability bias. People eat about 50 per cent more than they say, and exercise about 50 per cent less than they believe.
Similarly, perception of obesity is very inaccurate, with only ten per cent of obese subjects recognising their own obesity. Studies of perception of physical fitness have shown no relationship at all between perceived fitness and actual fitness level.
Losing weight requires strong motivation and great self-discipline – and motivation requires an acceptance of reality. Obese people are unlikely to be motivated if they do not see themselves as obese, and unfit people will not be motivated to take up exercise if they consider themselves to be fit.
As I said, easier said than done. I am etc,
Hugh Bethell MD FRCP, Alton, Hampshire