Eat less and exercise more--it has long been a magic word for reducing those extra weight. But now it seems that all the hard work may have been in vain. Scientists say there are ten other reasons why people just keep getting bigger. They say that sleeping habits, central heating, medicines and even some pollutants   can play a role in weight gain. Traditionally, people have focused on diet and exercise to solve the problem. However the scientists from top US and Canadian universities say that other things must be considered. Lack of sleep could be partly the reason. In recent years, the average night's sleep has dropped from nine hours to just seven. Sleep shortage changes levels of the hormones   that control food intake and body fat and increase hunger and appetite. If it is too hot or too cold, we burn calories   to cool down or heat up. But if the temperature is just right, the calories may be turned into body fat instead. Those who take medicine to control their blood pressure can often put on weight. Similarly, studies have shown that going on the Pill can add to a woman's weight. Mother nature may also be the reason, with our body shape being partly inherited  . The overweight are also more likely to settle with partners of a similar size. And their children are more likely to be obese  .  And the use of pollutants is on the rise, say the researchers. The man-made chemicals in pesticides   and plastics can lead to weight gain. Your mother's age and your weight at birth are also important, with older woman more likely to have obese children and underweight babies having a bigger chance of being obese in later life. We also tend to put on weight as we get older. Finally, giving up smoking can also help pile on the pounds. The scientists from Yale, Cornell and Johns Hopkins said there was some evidence supporting poor diet and lack of exercise as the main causes of obesity. Which of the following factors doesn't lead to overweight?
Regular and enough sleep. Comfortable living environment. Not enough physical exercise. harmful chemicals in the food.