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Depression and Insulin Resistance: An Obstacle to Weight Loss

Insulin resistance may make dieting very difficult.

Diets work when you don’t have more than 10 or 20 pounds to lose. It makes sense: You do not routinely eat gigantic amounts of food so diet size portions are acceptable; you are not so heavy that exercise is difficult, you are not subject to the emotional distress of fat shaming, most of the people you know also have to lose that several pounds, and most important, you probably don’t have insulin resistance and the depression that is often associated with it.

But for those who are obese, attempts at weight loss are complicated not just by having to decrease quite significantly the amount of food they are allowed to eat and having to start or increase their physical activity; they also may have insulin resistance. And insulin resistance may make dieting very difficult.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, insulin resistance occurs when the cells in your body such as muscle, fat and liver become insensitive to insulin and are unable to bring the blood glucose into their cells to use for energy. When this occurs, the pancreas, the organ that makes insulin, continues to make more so that eventually enough glucose gets pushed into the cells. Insulin resistance often leads to a prediabetic state whereupon the pancreas is unable to make enough insulin and glucose levels in the blood remain higher than normal. According to the CDC, about 1 in every 3 adults in the U.S. is prediabetic.

Sometimes insulin resistance is a consequence of obesity but may be caused by certain medications, and/or a concurrent condition of polycystic ovary syndrome, gestational diabetes, Cushing syndrome, sleep apnea, high blood pressure, and abnormal cholesterol levels. Although many causes of insulin resistance may be hard to overcome, the National Institute of Diabetes and Digestive and Kidney Diseases website recommends lifestyle changes such as weight loss, increased exercise and better diet to try to reverse the disorder.

Of course, these suggestions match those recommendations used to support weight loss efforts in general: a calorie-restricted, nutritionally adequate food plan and an exercise program compatible with the physical ability of the dieter. But these suggestions fail to mention that insulin resistance often is accompanied by unwelcome mood changes that might affect the ability of an individual to carry out these suggestions. There is now considerable evidence that insulin resistance and depression are often linked.

The obese individual who has insulin resistance is being asked to lose weight while feeling depressed, exhausted, disinterested in social interactions, unable or unwilling to exercise, and struggling with a sense of hopelessness. If the depression is treated with antidepressants, the patient may gain more weight, as this is often a side effect of antidepressant treatment.

There is very little understanding of how the inability of the cells to take up glucose without requiring abnormal amounts of insulin could have an impact on mood. One explanation may be found in a study conducted many years ago that measured the levels of specific amino acids (the components of protein), insulin, and glucose in the blood of normal and obese women after they consumed an afternoon snack of carbohydrate. The researchers knew that after normal-weight individuals eat carbohydrates, insulin drives all the amino acids out of the blood and into the cells along with glucose; that is except for one amino acid, tryptophan. This has a direct effect on the brain’s ability to make serotonin. When the levels of the other amino acids are high, tryptophan doesn’t get into the brain and no serotonin is made. But after insulin reduces the levels of the other amino acids in the blood, tryptophan is able to enter the brain, and is quickly converted into serotonin.

However, none of this happened with the obese individuals in the study. Insulin was unable to remove the amino acids from the blood and send them into the cells after they ate carbohydrates. This meant that tryptophan could not enter the brain, and most likely, no serotonin would be made.

Is it possible that a prolonged period of insulin resistance might gradually decrease the amount of serotonin in the brain and contribute to depression? We know that serotonin also controls satiety; that feeling of fullness that makes one stop eating. Are people with insulin resistance, and possibly too low serotonin levels, unable to feel full and therefore continue to eat more than they should?

Is it any wonder that weight loss is so hard for someone whose excess weight causes insulin resistance? Weight loss programs do not address the problems of depression, and perhaps the inability to feel full, due to insulin resistance. Weight loss programs that restrict carbohydrates are in a sense adding fuel to the fire, because if carbohydrates are not eaten, serotonin is not made, and the depression may persist. And weight loss programs that do not emphasize the importance of exercise should be avoided, since exercise is one of the best ways to reverse insulin resistance. The consensus among specialists dealing with insulin resistance is that a patient with insulin resistance must exercise at least 30 minutes a day, five days a week.

Carbohydrates should not be avoided, but those that are digested slowly are best as they do not require high levels of insulin to be released as glucose enters the bloodstream. High fiber carbohydrates like beans, lentils, high fiber cereals and bread, brown rice, buckwheat groats, farro, and other high fiber grains are good choices. All sugary and processed carbohydrates like those in snack foods must be avoided. As weight begins to be lost, insulin levels usually return to normal. Dieting may become easier with time; moods will improve and a sense of fullness after eating diet size portions will be noticed.

Those who are able to lose weight while dealing with depression and the absence of satiety are to be congratulated; it is no small achievement.