Weight Loss Goddess

Set point theory

According to this theory, you have a predetermined weight and level of body fat—called a set point—that your body wants to maintain.

This body fat level is determined by genetics, just like your height.

Exactly how the body controls its fat stores is unknown, but the regulatory mechanism, sometimes called the adipostat, (like a thermostat for fat) is located in the brain. The adipostat monitors the body’s fat stores, possibly through the actions of the hormone leptin, and works to maintain the set point by adjusting appetite, physical activity, and resting metabolic rate to conserve or expend energy. Thus, eating and physical activity may be subtly controlled by the set point mechanism.

Metabolism continued

Whether or not obese people have an abnormally slow metabolism is controversial.

In fact, it takes more energy to maintain a greater body mass. For example, a person who weighs 200 lbs has a higher resting metabolic rate than someone who weighs 150 lbs.

In addition, the 200-lb person expends more calories than the 150-lb person for any given physical activity. But even when people of the same height, weight, age, gender, and muscle mass are compared, their resting metabolic rates vary by 20% or more.

This means that if you are predicted to use 1,200 calories through your resting metabolic rate, you may actually use anywhere from 1,080–1,320 calories. This variability explains in part why two people who weigh the same may require different amounts of calories to maintain, lose, or gain weight.

It’s important to remember that whatever your resting metabolic rate, if you consume more calories than you expend, those extra calories will be stored primarily as fat.

This will happen regardless of whether the extra calories come from fats, carbohydrates, or proteins (although dietary fat is converted into body fat more efficiently than dietary proteins or carbohydrates).

For more information on metabolism and how it is possible to boost it, see the Metabolism section of this site.

 Metabolism
This is the process that extracts and utilizes energy (measured in calories) from food. Even at rest, energy is needed for many functions, such as breathing, the beating of your heart, and cell growth and repair.

The amount of energy used for these basic functions while you are at rest is known as your “resting metabolic rate,” which accounts for approximately 70% of your body’s use of energy each day. The rest is taken up with the physical exercise you do each day to expend calories. The more activity, the more likely you will be to lose weight, but your metabolism can be a trick beast to deal with.

Your resting metabolic rate is affected by your weight, age, level of physical activity, and the amount of muscle in your body. Having more muscle increases your metabolic rate, since muscle utilizes more energy than fat, even at rest.

This is why people who used to be athletes often pack on the pounds when they stop competing, and why many of us start to suffer from ‘middle aged spread.’

Your resting metabolic rate is also in part genetically determined.

The act of eating also uses up energy, because energy is needed to digest food, absorb nutrients, and store excess calories as body fat. This process—called thermogenesis—accounts for 10–15% of the body’s total daily energy expenditure.

Some research suggests that obese people require slightly less energy for thermogenesis than normal-weight people, and thus more of the calories they eat are stored as fat rather than used to process food.

Genes

A number of genes are responsible for regulating body weight.

More than a decade ago, researchers at Rockefeller University discovered that mutations in a gene called the obesity (ob) gene prevented a strain of mice from producing leptin.

Leptin is a hormone normally manufactured by fat cells, and released into the blood to inform the brain about the body’s level of fat stores.

When this communication system works properly, the brain responds to leptin by reducing a person’s appetite and speeding up metabolism to maintain a normal level of body fat.

Because the mice with the mutated ob gene did not produce leptin, their brains continually sent messages to the rest of the body to eat and store fat, and the mice  became obese.

However, when leptin was injected into the obese mice, they quickly lost weight through a combination of decreased food intake and increased activity.

Since this discovery, however, researchers have found that administering leptin to obese people rarely reduces weight, because their blood leptin levels are already high.   It can also be because they have gone for so long not feeling full, that their eating habits are automatic and thus not easily undone.

Still, unraveling the link between leptin (and other substances released by fat cells) and weight may lead to the development of more effective drugs for weight loss by deaing with the center of the brain that signals satiation and fat storage.