Factors stronger than personal discipline influence body weight

Article Published: Nov. 1, 2012 | Modified: Nov. 1, 2012

Mood swings, acne, age-related issues and a host of health problems are often blamed on hormonal changes.

We now know that hormones, as well as metabolic pathways that stimulate and inhibit appetite, make permanent weight loss nearly impossible. Ninety percent of people who lose weight gain it back within a year.

In 1994, scientist Jeffery Friedman discovered leptin, a hormone secreted by fat tissue in proportion to its mass. Leptin tells the brain that there is enough energy stored in fat cells for the body to engage in normal, metabolic processes, such as eating a normal amount of food and exercising. Leptin is the way fat cells tell the brain that the energy thermostat is set right.
When people diet, they eat less, and their fat cells lose some fat, which then decreases the amount of leptin produced. Each person has a different leptin threshold. When leptin goes below that threshold, the brain senses starvation.

The body knows when it has dieted. Leptin level falls and provide a stimulus to eat more. For most people, the power of the biological system wins over the drive to be thin.

Obese people have large amounts of leptin, but their brains aren't getting the important signal to stop eating, due to leptin resistance. Leptin resistance is similar to insulin resistance in type 2 diabetes, in which the pancreas produces large amounts of insulin, but the body doesn't respond to it properly.

Leptin is also part of the body’s reward system. When levels are low, food is even more rewarding. When leptin levels are high, food doesn't look nearly as good.

In leptin-resistant people, the reward system doesn't cue a person to stop eating when leptin levels rise. The leptin is being made by the fat cells, and the fat cells are trying to tell the brain that it’s time to quit eating, but the brain can't get the signal.

According to Friedman, variation in body weight may be as genetically influenced as height. There is a biological system that keeps people within a 15 pound range. The lower end of that range may be achieved for better health. The further one attempts to move outside the range, the more difficult it gets. The experience that someone has trying to lose 50 or 100 pounds is not the same as someone losing five or 10. Eating a healthy diet and exercising is good for health and should be encouraged, but we are in some ways captive in the body configuration that we have.
The prevalence of obesity has been climbing steadily since the late 1970s, due to the constant availability of relatively cheap, high-calorie food. People on the thinner end of the range have remained so, and the heavier have gotten even heavier.

For most of history, people with the ability to take in many calories and store them were more likely to survive through famines and to pass on their genetics. Our genes haven’t changed over the past 40 years, but our environment has.

With many biological mechanisms in place that make weight loss so difficult, an ounce of prevention is worth more than a pound of cure. Rebelling against our toxic food environment and feeding our children a healthy diet so they don’t become obese is the most loving gift we could ever offer.

Margie Mansure, M.S., R.D. is a registered dietitian/nutritionist and extension agent with N.C. Cooperative Extension. She offers personalized classes to improve the health of citizens in Watauga County through worksites, schools and community groups. For more information, email margie_mansure@ncsu.edu or call (828) 264-3061.

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