There are several hormones that impact how many ingested calories are stored as body fat. If any of these hormones are out of balance, a person can gain weight even though they may eat less food. One hormone that exerts a significant effect on hunger and fat storage is insulin.
Insulin is produced by beta cells in the pancreas mainly in response to high levels of glucose (sugar) in the blood. Insulin enables the liver to store excess serum glucose. Insulin also stimulates the liver to form fatty acids that are transported to adipose cells and stored as fat. The net effect of insulin is the storage of carbohydrate, protein, and fat in the body.
A poor diet can induce the pancreas to secrete large amounts of insulin. Aging people also experience metabolic disorders that cause the hypersecretion of insulin. Eventually the cells in the body become resistant to insulin (by decreasing the number of insulin receptors).
As cells become insulin resistant, the body stabilizes blood glucose by producing higher levels of insulin. The effect of high insulin production is weight gain. The long-term result is often Type II diabetes in which blood glucose levels become unstable even though insulin levels remain dangerously high.
As people accumulate excess body fat, they develop a chronic condition known as hyperinsulinemia, meaning the pancreas constantly secretes too much insulin and the body is unable to effectively utilize it.
A novel approach to fat loss has been developed based on the established fact that overweight people have too much insulin in their blood. Insulin causes sugar and dietary fats to be converted to body fat. Excess insulin prevents stored body fat from being released, even when a person undergoes severe calorie restriction, such as in crash dieting.
Poor diet, obesity, aging, and metabolic disturbances result in the excessive secretion of insulin, a factor in the development of Type II diabetes. Suppressing excess insulin production is a crucial and often overlooked component of a fat-loss program.
The role of excess insulin in causing weight gain has been an accepted scientific fact for years (Beeson et al. 1971; Woodward et al. 1989; Heller et al. 1994). Building on this observation, some scientists have postulated that it is impossible for people to lose significant body fat as long as they have insulin overload.
A noticeable effect of surplus serum insulin is constant hunger, which results in a vicious cycle in which overeating causes more and more body fat to accumulate, which in turn causes even greater amounts of unwanted insulin to be secreted from the pancreas. We now know that hyperinsulinemia predicts diabetes mellitus (Haffner et al. 1990; Kekalainen et al. 1999; Weyer et al. 2000). Even in children, serum insulin levels are far higher in obese than in non-obese children of the same age.