The hormone leptin can play a major role in keeping your metabolism up and running, and your weight in check after you’ve shed a few kilos.
This time of year typically sees a lot of people embarking on a weight-loss mission. The problem is that although many people shed the kilos successfully, as many are likely to regain that weight. Why? Well, a big part of the answer appears to be that when we lose weight, the body brings into play a range of mechanisms to help it body preserve its ‘ideal’ mass.
One of these is a general dampening of the metabolism. “After weight loss, there is a decline in energy expenditure that reflects both the loss of metabolically active tissue plus an additional 300 to 400 calories per day, which may be termed ‘adaptive thermogenesis’..”
In other words, your metabolism reduces to an extent greater than is expected, solely as a result of weight-loss. For example, while body-weight declines by, say, 10 percent, your metabolism may drop by 15 percent or more.
The study authors go on the add: “Decreased energy expenditure after weight-loss would have little consequence if it easy to sustain a corresponding reduction in energy intake to maintain a reduced body-weight. As anyone who has attempted to sustain weight-loss can attest, this is not the case”.
Some of the mechanisms at work here include reduced activity in a part of the nervous system called the ‘sympathetic’ nervous system. There are also changes in hormones that affect the metabolism, including production of thyroxine and leptin.
Leptin is a particularly interesting hormone. It is secreted by fat cells and acts on a part of the brain called the hypothalamus in order to speed up your metabolism and suppress appetite.
As we gain weight and accumulate fat, more leptin is produced (in theory) to help keep things in check. When we lose weight, those levels generally fall, which can stifle our metabolism. It can also make people feel hungrier. One of the ways this manifests itself is as a reduced satisfaction from food. In other words, for a given amount and type of food, people tend to feel less satisfied once they’ve lost weight they’ve lost weight than they were when they were heavier. The risk here, of course, is that people may then be driven to eat more.
The journal paper featured an experiment designed to assess the effect of leptin on people who had lost weight. Ten obese individuals were fed a liquid diet offering 800 calories a day until they had lost about 10 percent of their weight. This took anything from 36 to 62 days, and their metabolism was measured before and after weight-loss. The individuals were also tested in terms of their response to eating and how satisfied they felt after consuming food.
After weight-loss, on separate occasions, individuals were injected with lepin or a placebo for five weeks each.
- Total calorie burn fell by about 700 calories a day due to weight-loss when individual were injected with the placebo. However, with lepin,the reduction was much less-about 400 calories a day.
- Calorie metabolism per kilo of ‘lean mass’ (muscle) also fell as a result of weight-loss, but this was not the case when leptin was being administered.
In short, lepin helped people maintain their metabolism after weight loss-just as we’d expect. Plus, when the individuals were on leptin, they derived more satisfaction from their food.
What we have here is evidence that we stand a better chance of losing weight and keeping it off if we have well functioning leptin. Problems in this department-also known as ‘leptin resistance’-are now emerging as a major factor in weight-control issues. Inflammation in the hypothalamus appears to be one cause of leptin resistance. And one thing we can do to prevent this is to avoid foods that are inflammatory in nature. Spikes in blood sugar promote inflammation, so this is yet another reason for not eating a diet based on blood sugar-disruptive carbohydrate including many starchy staples.