breaking the obesity cycle
Jenny Bryan and Rachel Newcombe
realistic goals
'We need to encourage overweight and obese people to lose 5-10% of their body weight over a year, and to maintain it. Research has shown that those who are most successful make several small adjustments to their weight and exercise pattern. We live in a "quick fix" society but losing and maintaining weight loss is a slow process,' says Dr Hill.
Instead of trying to stick to harsh diets, he recommends that people who are overweight take small steps towards greater control of their food intake – substituting a piece of fruit for a chocolate biscuit as their mid-morning snack, changing their choice of food at mealtimes, reducing the amount of food they eat outside the home, developing a new social life around sports or exercise.
'If all the people who are overweight or obese could just lose half a stone as part of such changes we would see important improvements in public health and, at a personal level, these people would feel much better about themselves, about being in control of their eating and improving their social activities,' Dr Hill points out.
Crash diets may achieve short-term weight loss but, without a change in long-term eating and exercise habits, it's unlikely to stay off. Some specialists believe that people with a serious weight problem – and their doctors – aim too high, too fast.
An obese woman who is 5'6" and weighs 190 pounds (86kg) may be disappointed if she only loses 20 pounds (9 kg) because her BMI will still be 27.5 – making her overweight. But she has achieved a 10% fall in her bodyweight – something which the World Health Organisation recognises as a significant achievement. Indeed, it considers that a 5% fall in bodyweight is well worth having.
Dietitians recommend trying to lose 1-2 lb (0.5-1 kg) per week – something which requires a change in energy balance of about 1,000 kilocalories per day.
Ideally, this should be done through a combination of eating less and taking more exercise. Energy intake can be reduced by about 500-600 kilocalories and energy expenditure increased by about 400-500 kilocalories. Women and inactive men need about 2,000 kilocalories per day to stay the same weight, men and very active women about 2,500 kilocalories. So a reduction of about 500 kilocalories in food intake is far from starvation rations.
The first few days of a diet can be very encouraging, and people often find they can lose more than 1 kg in their first week. This is because early weight loss has more to do with reduced water and glucose stores (glycogen) than loss of fat. Quite simply, reducing your food intake by 500 kilocalories gives you a bigger weight loss when you're using up glycogen than when you're using fat. When you're burning glycogen, you'll lose about 1kg for every 1,000 kilocalorie deficit you manage to achieve in energy balance.
But you'll only start to break down fat once glycogen stores are depleted and, when you're burning fat, you'll need to achieve an energy deficit of 7,000 kilocalories for every 1kg you lose in weight. So after that first week on the diet, your weight loss will probably fall back to the target of 1kg per week.
Whatever diet you choose in order to reduce your calorie intake, be sure it stays within the overall rules of healthy eating, low on fat, high on carbohydrate, fruit and fibre. Aim to eat three meals a day. If you miss meals, you're more likely to feel hungry and need to snack. Dieting is not just about losing weight, it's about establishing a healthier pattern of eating which you can continue long after the diet is over.
(July 2001, resources updated March 2005)
