Reviewed by Robert Ehrman, MD
Your body and weight loss
When you start to lose weight, you lose some of your stored fat. That may seem like a good thing to you, but your body doesn’t always agree. We used to think fat just sat in your body and did nothing. But we now know that is not true. The fat you store makes hormones that help control your weight and hunger.
The role of Leptin
Leptin is a hormone made in the fat cells that goes through your bloodstream to your brain. Leptin tells your brain when you are full so that you stop eating. The more overweight you are, the more leptin your body makes. Over time, your body becomes resistant to these very high levels of leptin. The leptin is blocked from giving your brain the message that you are full. In addition, food is less rewarding when you are resistant to leptin. You eat more, enjoy it less and still feel hungry.
As you lose weight, your leptin levels begin to drop. Because of this, your body thinks you are starving. Your metabolism slows down and tries to hang on to the fat you have stored. Other signals also tell your brain you are hungry, so you want to eat more, as well. In some ways, you fight with your body when you try to lose weight. Unfortunately, you can’t take leptin to lose weight. Leptin is a protein and would be broken down in the stomach before it could get into the bloodstream.
Your set-point weight
The other thing to keep in mind is that some experts believe everyone has a built in control system that decides how much he or she should weigh. This set point is different for everyone and is set by your genes. That’s why it is easier to lose weight when you begin dieting than later on in your weight-loss efforts. You may do the same things, but you stay at the same weight or even regain what you lost. Your metabolism slows down because your body is trying to get back to your set-point weight.
The set-point also affects how many calories it takes to maintain your weight. If you lost weight and now weigh 150 pounds, you will need fewer calories to maintain that weight than a person who has always weighed 150 pounds.
And now for the good news: Although it may sound impossible, you can lose weight and keep it off. Exercise helps lower insulin resistance, which can decrease leptin levels. Exercise can also help increase your metabolism and fight your body’s resistance to weight loss. It isn’t easy and it isn’t as simple as others tell you, but it can be done.