Heart disease could be developed as a result of over-weight or obesity, which is usually due to unhealthy diet, excessive eating, and lack of exercises. If I tell you that inadequate sleep for a long period of time, you will actually gain weight. Do you believe it? In the mind of most people, chronic sleep deficit should naturally lead to a loss of weight because the body does not have enough sleep and there is an exhaustion of vitamins and minerals. But the two research studies conducted in 2004 reported otherwise: chronic sleep deficit can lead to over-weight or obesity.

As a matter of fact, there has already been link between sleep loss and weight gain established by previous researchers, but these two studies further suggested that the mechanism could be metabolic hormones that regulate appetite and tell the body when it has had enough to eat.

One of the studies reported that sharp fluctuations in the blood levels of the hormones ghrelin and leptin in people who consistently slept five hours a night, compared to those who slept eight hours. As compared to the control group, the sleep-deprived group experienced a 14.9 percent increase in the amount of ghrelin, an appetite-stimulating hormone, and showed a 15.5 percent decrease in the level of leptin over a long-term study on sleep habits and disorders of more than 1000 people.

Low level of leptin is an indication for starvation and increased appetite. The research also found that the sleep-deprived group had their body mass index, a measure of obesity, increased.

In the second much smaller study, a dozen healthy young men who were allowed to sleep just four hours a night for two nights also experienced similar dramatic hormonal changes. The men's leptin levels dropped 18 percent yet their ghrelin levels raised 28 percent. The men also clearly showed a desire for calorie-dense, high-carbohydrate foods.

Having not enough sleep has no direct link with heart disease, but over-weight could well be a risk factor for heart disease. So if you have a habit of staying very late for TV, computer games, Internet chat or any other matters, perhaps it is time for you to consider adjust your sleeping habit. Or if you have very good reasons for staying late, you probably need to remind yourself that you should watch out your diet: don't eat whenever you feel hungry! It could be the effect of fluctuation of ghrelin and leptin in your body.