Leptin Might Be The Key To Weight Loss and Maintenance
June 25, 2008
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One of the problems when dieting is that after the while the body adapts to the lower calorie intake. After a period of restricted food intake the body starts to make changes in some of its systems.
When calories have been in short supply for a while, the body increases the feelings of hunger. This is a basic survival mechanism and would make our prehistoric ancestors go out and find some berries or go hunting a woolly mammoth. We need to eat to survive. Unfortunately dieting also triggers this survival mechanism, and stimulates an overfeeding response.
Additionally, after a period of restricted calories our metabolism slows down. This, too, is a survival mechanism. In times when there is a shortage of food, if the amount of energy that the body uses can be reduced, we are more likely to survive until there is adequate food again.
These two changes in the body result in it becoming harder to lose weight after dieting for a while. Importantly, it also makes it harder to maintain the weight loss after losing the desired weight.
Leptin is a hormone that is secreted by fat cells. It is involved in a number of processes in the body including energy regulation. During fasting, the levels of leptin circulating in the body drop. This drop in leptin levels has a range of effects that include reduced energy expenditure and the stimulation of overfeeding.
Several studies suggest that a potential treatment option for weight loss and maintenance may be leptin or some future drug that increases the levels of leptin. The studies looked at both energy expenditure and brain activity in response to food stimuli.
The first studies compared markers of energy expenditure, with and without, an injection of leptin under the skin for those on a weight loss program. The leptin injection increased the circulating leptin levels to those pre-diet, and at the same time increased the levels of the markers of the body metabolism. So increasing the levels of leptin reversed the slowing of the body metabolism. This is likely to increase the rate of weight loss, and be important for weight maintenance.
The second study looked at brain activity. In certain areas of the brain after being on a diet for a while there is increased activity, which correlates with an increased appetite. In those who received leptin, the brain activity decreased to the level found prior to dieting. This suggests that increased leptin levels may decrease the feelings of hunger and make overfeeding episodes less likely.
These studies have several potential implications. As stated above, would treatments that increased leptin levels be useful in the latter stages of weight loss and for weight maintenance? (Note: The majority of obese individuals have high levels of leptin and are leptin-resistant so treatment is unlikely to work for them, unless they are on long term calorie restriction. For those who are obese and have low leptin levels, it certainly could be a treatment option.) Additionally, do low levels of leptin predict obesity later in life? Would measurement of leptin levels help target those who have a high likelihood of gaining weight?
It is likely in the future that some form of leptin therapy may be of benefit to a significant number of people, particularly for weight maintenance.
The research has been published in the Journal of Clinical Investigation and is authored by Rosenbaum et al. For more details there is an excellent free access commentary in the issue as the most recent article.
Technorati Tags: leptin, weight loss, weight maintenance, slow metabolism, appetite, overeating
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[…] Ghrelin is a hormone that increases when we are hungry and decreases after we have eaten. This is the reverse of the appetite control hormone called leptin, which is low when we are hungry and high after a meal. A previous post talked about how leptin might be the key to weight loss and maintenance. […]