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We stand a better chance of losing weight and keeping it off if our leptin is functioning as it should. (Photos.com)
This time of year will see a lot of people trying to shed excess weight. Although many people will lose weight successfully, almost as many will regain that weight.
Why? A big part of the answer is that when we lose weight, the body brings into play mechanisms that help the body preserve its weight. One of these is a slowing of the metabolism.
Here’s how the authors of a paper published online on Jan. 11 in the American Journal of Clinical Nutrition describe it: “After weight loss, there is a decline in energy expenditure that reflects both the loss of metabolically active tissue plus an additional 300–400 kilocalories per day, which may be termed ‘adaptive thermogenesis.’”
In other words, metabolism reduces to an extent greater than is expected solely as a result of weight loss. For example, while body weight declines by 10 percent, say, metabolism may fall by 15 percent or more.
The authors go on to add: “Decreased energy expenditure after weight loss would have little consequence if it were 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 include reduced activity in the sympathetic nervous system and changes in hormones that affect metabolism, including thyroxin and leptin.
Leptin is secreted by fat cells and acts on the hypothalamus to speed the metabolism and suppress appetite. I first became aware of the importance of this hormone by reading Stephan Guyenet’s blog: WholeHealthSource.blogspot.com.
As we gain weight and accumulate fat, more leptin is made to help keep things in check. When we lose weight, leptin levels fall, which can stifle the metabolism. The drop can also make people hungrier.
One of the ways this can manifest is 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 than they were when they were heavier. The risk is that people may then be driven to eat more.
The paper published on the Jan. 11 featured an experiment designed to assess the effects of leptin on people who had lost weight. Ten obese individuals were fed a liquid diet of 800 calories a day until they had lost about 10 percent of their weight. This took from 36 to 62 days.
Metabolism was measured before and after weight loss. Also, individuals were tested in terms of their response to eating, including how satisfied they felt after food.
After weight loss, on separate occasions, individuals were injected with leptin or placebo (five weeks each).
• Total calorie burn fell by about 700 calories a day due to weight loss when individuals were injected with placebo. But with leptin, the reduction was much less, about 400 calories a day.
• Calorie metabolism per kilogram 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, leptin helped individuals maintain their metabolism after weight loss just as we’d expect. Plus, when the individuals were on leptin, they derived more satisfaction for a given amount of food.
We stand a better chance of losing weight and keeping it off if we have good-functioning leptin. Problems with leptin functioning, also known as leptin resistance, are now emerging as a major factor in weight-control issues.
Inflammation of the hypothalamus appears to be one cause of leptin resistance. One thing we can do is to avoid foods that are inflammatory. Spikes in blood sugar promote inflammation, so this is another reason for not eating a diet based on blood-sugar-disruptive carbohydrates, including many starchy foods.
Dr. John Briffa is a London-based physician and author with an interest in nutrition and natural medicine. His website is DrBriffa.com.
