CHAPTER 11

Our Fat Helps Keep Us Fat

Getting rid of body fat, called adipose tissue, is harder than we might realize

PART 1 Fat Does Not Just Sit There

Body fat is not dead weight. The activity going on in our adipocytes, or fat cells, never stops. Adipose tissue secretes hormones, including leptin, an appetite-control hormone, and adiponectin, associated with insulin sensitivity. The fat that surrounds our digestive organs, called visceral fat, is much more dangerous to our health than subcutaneous fat, the soft piles of padding beneath our skin. READ MORE

Your fat cells have important work to do. First of all, they store energy for your body to use as fuel. Fat cells also secrete the hormone leptin, which signals your brain when you do not need to take in any more energy because you have enough stored in your cells. Obese people typically have excess leptin circulating in their bloodstream, because the feedback system goes haywire when people ignore leptin's message to stop eating. When leptin was first identified, researchers were hopeful that it could be used to treat obesity—a substance that could signal the body to stop storing fat seemed too good to be true! It was. When leptin levels get too high, the signaling process gets short-circuited. The body becomes leptin resistant. “When we flood the body with leptin, the brain no longer listens,” says Dr. Philipp Scherer, director of the Touchstone Diabetes Center at the University of Texas Southwestern Medical Center. Neurons in the hypothalamus lose their sensitivity to leptin, and appetite control goes out of whack.

When we are overweight, our fat tissue lowers the blood levels of a second hormone, adiponectin. One beneficial aspect of adiponectin is that it has an anti-inflammatory effect on blood vessels, so that the lower levels seen in obesity increase the risk of heart disease; adiponectin is also a factor in the insulin response, associated with a healthy, efficient response to a rise in blood glucose levels. LESS

PART 2 Fat is Good at Sticking Around

Research Report

The Fat Came Back

By late adolescence or early adulthood, humans have their full complement of fat cells. We cannot easily reduce the number of fat cells we have, once we are adults. If we lose weight, fat molecules leave the fat cells and the cells shrink. But fat cells remain in place, ready to soak up fat again when our diet makes it available. READ MORE

Once fat cells stake out territory in the body, they hold fast. When we lose weight, owing to life style changes such as a more healthful diet and regular exercise, fat cells give up some of their occupants—fatty acids—which are burned for fuel. But the cells are still there, like shrunken balloons. The availability of more fatty acids, which can be transformed and stored as triglycerides, is all it takes for these cells to plump up again. Researchers have found that even surgical removal of subcutaneous fat does not improve our health considerably. The remaining fat cells pack in more fat, it's just in a different location of the body (see “The Fat Came Back”). LESS

PART 3 How to Break the Cycle

Just the Facts

The Leptin Cycle

Even if you are not seriously overweight, you should still be aware of the nature of fat and how it works in our bodies Throughout our lives, the fat composition of our bodies changes, and it's important to understand why. If you are overweight or obese, you can shrink your fat cells by altering your diet so that you are secreting less insulin and burning more fat. READ MORE

Women tend to have more active lipoprotein lipase (LPL) molecules taking action on their hips, behinds and thighs, especially when they are of child-bearing age. Around menopause, hormonal changes trigger heavier activity on the abdomen. This is why men are more likely to be apple-shaped, carrying more abdominal fat. Women are more likely to be pear-shaped, with more padding on hips and thighs. Genetic differences account for some exceptions, but for purposes of procreation, our fat accumulation patterns have clear gender differences.

This means that cutting food intake (especially sugar), building muscle and exercising will not turn every human into a supermodel. Most of us are preprogrammed to keep some fat on our frames, because it has its job to do. However, keeping body weight in a healthy, normal range will cut your risk for cardiovascular disease, Type 2 diabetes, and many other serious illnesses. To help your body fat do its important job, you can't accumulate too much of it. LESS