Saturday, 20th June 2020


Changes in  body weight are decided by how much you eat and how much you do. Your weight is like your bank balance with calories replacing money but an opposite desirable outcome. Think of calories as money – the more you put in as food the richer or fatter you grow while the more you take out as exercise the poorer or thinner you become. There is a deluge of advice out there – about how different diets and different exercise regimes effect the outcome – but the inescapable fact is that weight loss only happens if you expend more energy with exercise than you absorb as food. 

Exercise for preventing obesity

Staying a normal weight is much easier than losing weight. Those who take regular exercise from childhood seldom become obese. From an early age they have developed  a balance between input and output which works for them. Some will eat more and balance this with more physical activity and some eat less and do less – in an entirely unconscious way by which body weight remains constant. There is no identifiable quantity for either input or output to attain balance, just equivalence. Unfortunately that balance is easy to lose and most people put on weight as the years roll by.

Obesity is not caused by a slow metabolism nor by big bones. It is caused by your energy intake being greater than your output. It has been suggested that food packaging should include the exercise required to work off the contents! The labels would not make comfortable reading – walking at between 3.5 and 4 mph burns off about 5 calories per minute – about 26 minutes of walking is needed to walk off a can of fizzy drink. A digestive biscuit might take climbing 25 floors of stairs and a quarter of a pizza fuels running for 43 minutes.

Exercise for losing weight

Most adults in the developed world weigh too much and for them (you?) the problem is much more difficult. Getting rid of unwanted weight is much harder than avoiding putting it on the first place. As anyone who has ever felt the need to go on a diet can tell you, it is extremely difficult to lose weight. Eating fewer calories than you expend in exercise is really, really hard – but it can be done. Some people have the will power to cut their food intake to the level at which they lose weight but by the time we reach adulthood our dietary habits are hard-wired into us and most people who lose weight by diet alone subsequently put it all back on again. Some can increase their exercise level to the point where they lose weight but this does need a lot of effort – you need to perform moderate intensity exercise for an hour a day or run more than 15 miles per week to guarantee to lose weight without changing what you eat.

It takes a lot of formal exercise to reduce weight because such sessions occupy a very small proportion of our waking hours. Expending energy intensively for say 75 minutes a week can be easily overshadowed by being slightly less active for the remaining 6,720 minutes of the week. The 75 minutes of vigorous exercise can be cancelled out by reducing the average expenditure for the rest of the week by about 5% – or by surrendering briefly to the appetite stimulating effects of your physical efforts.. So, just as important as formal exercise for increasing energy output is the level of activity of day-to-day living. There is a host of ways in which you can increase your energy expenditure including walking upstairs instead of taking the lift, walking up the escalators, getting off the bus a stop earlier than your destination, walking short journeys for which you might take the car etc etc.

And don’t forget the power of being a fidget, an important element in daily energy expenditure. People who fidget are thinner than those who don’t and the energy expenditure of fidgeting can be as much as 600 Cal per day. Being a fidget has a strong inherited component and it may be difficult to make yourself into a fidgeter – though special fidget chairs have shown some promise.

Combined diet and exercise

The most successful weight losing strategy therefore is through a combination of diet and exercise and, most important of all, maintenance of this changed lifestyle in perpetuity. The changes need to be at the level which can be comfortably sustained. Most people find it too difficult, perhaps because it means going hungry and taking an unaccustomed amount of exercise (which may increase the appetite). In a world where we are surrounded by too much high calorie food, such self-denial may seem close to masochism. Becoming more physically active does reduce the pain.

The Cochrane report on “Exercise for Overweight or Obesity, 2006” analysed the results of 43 studies involving 3476 participants. Overall they found a modest effect of exercise programmes without dietary changes – with weight losses between 2 and 7kg. More vigorous exercise was more effective than less vigorous. However the most effective treatment was a combination of diet and exercise, with diet alone being rather more effective than exercise alone.

More benefits from using exercise

Those who use exercise to lose weight gain another benefit – a reduction in risk factors for cardiovascular disease with lowering of blood pressure and blood sugar and an improvement in blood lipids. These improvements are seen even in those who take up exercise but fail to lose weight, a fact which is confirmed by studies which have shown that while both BMI and fitness are strong independent predictors of all-cause mortality, fit obese patients have a lower mortality than the unfit people of normal weight. Unfortunately very few obese people take enough exercise to counteract the ill effects of obesity – one estimate calculated that just 2.2% of all men and 4.1% of all women in England could be classed as both obese and fit.

The other great benefit of using exercise as part of your weight control programme is that it helps to maintain and increase your musculature – starvation diets are no respecters of which part of your body shrinks. Fat is not the only part to be diminished as can be seen in the pictures of the victims of famines or wartime privation. Exercise training increases muscle mass – and muscle is somewhat more dense than fat. Those who fail to lose weight during exercise programmes may have lost fat but it has been replaced by muscle. One meta-analysis involving 4815 subjects found that in the absence of weight loss, exercise produces a 6.1% decrease in visceral adiposity (ie paunch size), whilst diet showed virtually no change (1.1%).

Different types of exercise

The way you exercise has an influence on its effectiveness. Moderate intensity exercise (MOD) has been compared with high intensity interval (HIIT) and sprint interval (SIT) training. All three regimes were associated with similar reductions in body fat percentages but interval training provided greater reductions in total fat mass. Since the time spent in MOD averaged 38 minutes, HIIT averaged 28 minutes and SIT averaged 18 minutes, the time saving of interval regimes might appeal to busy individuals.

Maintaining weight loss

Once weight has been lost by whatever combination of diet and exercise there is a depressing tendency for the weight to be regained – more than 70% of people who succeed in losing weight will have returned to their usual weight within two years. It takes about 275 minutes per week of moderate exercise to maintain weight loss – considerably more than the DoH recommendations for healthy living. However exercise is more effective than diet in maintaining weight loss. Those who are successful in maintaining a lowered body weight eat more than unsuccessful dieters but expend significantly more energy in daily activity.


The easiest way to lose weight is to combine eating less with exercising more. To keep it off, maintenance of the exercise habit is crucial. The trick then is to maintain your new life-style. Some doctors may prescribe pills which might help a bit but only in the short term. Weight losing groups such as Weight Watchers and Slimmers’ World can be helpful. The only guaranteed way, however, is surgery. This is now available under the NHS for a limited range of indications – but what a way to manage what is after all a lifestyle choice.


Exercise and migraine
I am repeatedly surprised by the range of conditions which can be reduced by becoming more physically active. A recent review of the evidence has found that “a sufficiently rigorous aerobic exercise regimen alone is sufficient to yield a statistically significant reduction in migraine frequency, intensity, and duration. Higher-intensity training appears to confer more benefit.” The effect is equivalent to that of prophylactic medication1.











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