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Potential Causes of Excessive Weight Gain

Weight gain is a result of imbalance between energy intake (calories) and the energy a person expends through metabolism and physical activity. Excess calories are then stored in the fat cells also called adipose cells. An individual’s total fat stores reflect both the number and size of fat cells in the body. The number of fat cells increases fastest during late childhood and early puberty. However, when the person consumes more energy than is expended, additional fat cells may continue to develop throughout their lifetime.

People who are obese have not only more fat cells but their fat cells are also larger than those in people who maintain healthy weights (check your BMI to determine a healthy weight range). A combination of high-calorie, high-fat diet and sedentary lifestyle is one of the main causes of excessive energy intake compared to energy output, an imbalance that ultimately leads to obesity. In fact, less than one-third of people in western society meet the basic activity level, which is defined as 30 minutes of exercise a day on most days of the week.

Genetics and Obesity

Genetics also seems to play their role in obesity. A child’s chances of being overweight are 40% if one parent is obese and 80% if both parents are obese. Two hormones play a part in the genetics that determines obesity: leptin and ghrelin. Leptin is a hormone made by fat cells that regulates appetite. If a person has consumed too many calories and is gaining weight, leptin levels increase to reduce appetite and increase energy use. And if a person is losing weight, then leptin levels decline to stimulate the appetite and limit energy use. Therefore, not producing enough leptin, increases the risk of being overweight. It should be noted here though that the point where a signal is sent to the brain to change leptin levels may vary considerably among individuals. This point is named the set point. Research has shown that obese people have a higher set point at which leptin is released, so they are biologically programmed to have a bigger appetite.

Moreover, obese people tend to have a lower basal metabolic rate (BMR is a measure of the amount of calories consumed at rest) and thus consume fewer calories at rest than lean people. When overweight people who have lower BMR attempt to lose weight by reducing their caloric intake and/or by exercising, their BMR declines to counteract their efforts to shed weight.

Ghrelin, on the other hand, is a protein that behaves like a hormone. Its role in weight regulation is to stimulate the appetite and thus maintain a stable body weight. Ghrelin is secreted mostly by stomach cells. Blood levels of this protein usually rise before and fall after a meal. When the body has a negative energy balance ghrelin levels are high, stimulating the appetite. This occurs for example when an overweight person goes on a diet. The high levels of ghrelin in individuals trying to lose weight may explain why achieving weight loss is difficult for them.

An enzyme called lipoprotein lipase has been shown to facilitate fat storage in both fat and muscle cells. Overweight people typically have more of this activity in their fat cells than slim people (men usually in the abdomen and women in the thighs, hips and the breasts). The hormones testosterone and estrogen influence the activity of lipoprotein lipase.

Other Factors Affecting Weight Gain

The development of obesity is complex and, therefore, various other environmental factors can lead to an individual becoming obese, including:

  • Age. As people grow older, the amount of muscle mass in the body decreases, which leads to a decrease in metabolism. In addition, older people tend to be less physically active. Individuals who do not reduce their calorie intake as they get older are therefore likely to put on weight.
  • Sedentary lifestyle. A physically inactive lifestyle can lead to obesity.
  • Medications. Certain medications have been linked to promoting weight gain, including corticosteroids and some drugs used to treat psychiatric conditions.
  • Alcohol. Consuming too much alcohol can lead to obesity because alcohol stimulates appetite.
  • Psychological issues. Some people eat, even when not hungry, as a way of dealing with their emotions.
  • Physiological factors. Metabolic rates vary from individual to individual. This means that two people with the same weight, body type and height may require a different number of calories to maintain a normal weight. A person with a slower metabolism will be more likely to have a weight problem.
  • Eating disorders. Many obese people who attempt to lose weight actually have binge eating disorders.
  • Medical conditions. Low thyroid function (hypothyroidism), an overproduction of hormones by the adrenal glands (Cushing’s syndrome), low metabolic rate, polycystic ovarian syndrome or other medical conditions can all lead to excessive weight gain. However, they account for a small percentage of all cases of obesity.
  • Pregnancy. Some women who put on weight during pregnancy may find it difficult to shed their extra pounds afterward. This extra weight may sometimes provide the foundation for additional weight gain which results in obesity.
  • Quitting smoking. People who quit smoking tend to gain weight that can eventually lead to obesity. This is mostly due to nicotine’s ability to raise a person’s metabolic rate. In addition, people who quit smoking may also turn to sweets to fill the smoking void, resulting in weight gain.
  • Lack of sleep. Lack of sleep, especially in children, may disturb metabolism and trigger obesity (see: Lack of Sleep Can Make You Fat).