Body Weight and Your Brain: How Do They Interact?

If you’re trying to lose weight, your brain may not be on your side.

Recent research suggests that the brain acts as a sort of weight regulator that seeks to maintain a “set point” of body weight and restore lost weight when you diet. Through various processes, the brain is involved in such key diet-related issues as feelings of hunger and satiation, levels of self-control, sense of reward associated with food, and metabolic rate and caloric needs. Scientists hope that finding ways to address and control these brain responses to weight loss might one day lead us to new therapies that can help people slim down and stay at a healthy body weight.

What Works?

“Simply reducing your calorie intake leads to increased hunger and a metabolic slowdown that impedes weight loss,” says Maurizio Fava, MD, executive vice chair of the department of psychiatry at Massachusetts General Hospital (MGH) and director of the division of clinical research at the MGH Research Institute. “There are other options that may be more effective.”

Dr. Fava suggests that leading a healthy lifestyle with regular exercise, good quality sleep, low levels of stress, and a sensible diet can help you drop pounds over time. Switching from the low-fat, high-carbohydrate American diet to a diet low in refined carbohydrates and replacing processed carbohydrates with nonstarchy vegetables, legumes, fruits, and whole grains can help people maintain healthy blood sugar levels and reduce feelings of hunger. Moderate consumption of saturated fats is acceptable, as long as these fats are balanced by healthier monounsaturated and polyunsaturated fats, such as those found in avocados, nuts, olive oil and flaxseed oil.

Losing weight can benefit brain health by reducing risk for insulin resistance, an impaired cellular response to insulin in which glucose levels continue to rise in the bloodstream while cells become starved of fuel. Insulin resistance can lead to cell injury or death, harm the hippocampus—a key memory region of the brain—and the dentate gyrus, a hippocampal sub-region associated with age-related memory decline. Avoiding obesity can also improve brain health by: normalizing the action of the hormone leptin, which regulates appetite and is thought to influence learning and memory; reducing levels of fat that produce proteins called cytokines, which promote inflammation and increase the risk for dementia; and reducing risk for cardiovascular disease, which can affect the blood vessels of the brain, clogging them with “bad” LDL cholesterol that impedes the circulation of oxygen and nutrients to brain cells.

 “Biggest Loser” Study

The brain’s role in weight gain and loss received national attention recently after the publication of research involving 16 contestants on the TV show “The Biggest Loser,” in which obese participants compete to reduce weight through an intensive program of dieting and exercise. The study’s findings, published online May 2, 2016 in the journal Obesity, suggest that the brain’s role in determining the body’s resting metabolic rate (RMR, the amount of energy expended while at rest) is a critical factor in the weight-loss process.

Researchers found that, six years after competing in the show, participants’ bodies had adapted to their weight loss with a persistent and significant slowing of their metabolic rate that continued for years. Essentially, contestants’ brains were engaged in an intense effort to help the body regain the lost weight by dramatically reducing the demand for calories. When participants had cut calories to maintain their new, thinner, bodies, the brain had slowed the RMR even more, burning so few calories that most participants gradually regained their weight.

Roadblocks

Biopsies of muscle tissue have demonstrated that an individual’s muscle fibers become significantly more efficient after the loss of 10 percent or more of body weight, burning 20 to 30 percent fewer calories while engaged in the same everyday activities and moderate exercise as before their weight loss.

The readjustment of RMR is just one of a number of changes the brain initiates in response to dieting that appear to complicate efforts to slim down. Deepening our understanding of RMR might uncover possible pathways to more effective weight control, as might learning more about these other weight-associated brain changes:

Hormonal changes. Levels of the hormone leptin, which suppresses hunger, drop significantly in people who diet, as do four other hormones related to feelings of hunger and satiation, according to a 2011Australian study. The researchers also found that participants who dieted had elevated levels of ghrelin, the “hunger hormone,” which increases the desire to eat. “We desperately need agents that will suppress hunger and that are safe with long-term use,” the lead researchers said.

Changes in neurotransmitters. Research suggests that decreased food intake may be associated with changes in dopamine, serotonin, and other neurotransmitters involved in feelings of pleasure and reward. These changes appear to boost the urge to seek out food, and may explain episodes of bingeing among dieters.

Reduced self-control. Scientists have used functional magnetic resonance imaging (fMRI) to observe dieters’ brain activity. They have found that compared to their brain patterns before losing weight, participants who lost weight showed greater activity in parts of the brain that are associated with reward when they looked at food, and less activity in parts of the brain involved with self-control.

Tips to Stay Trim

Although maintaining weight loss can be challenging, the following tips may be helpful when you’re dieting or trying to maintain a lower weight:

▶ Get a medical assessment to identify any health problems that may be leading to your excess weight, such as thyroid or insulin abnormalities.

▶ Don’t eat when you’re not hungry. Pay attention to your body’s signals—mindless snacking leads to weight gain.

▶ Get regular, moderate exercise. Experts recommend a minimum of 30 minutes per day, five days per week. Seize opportunities to engage in physical exertion throughout your day.

▶ Lower your stress levels. Use relaxation techniques, such as yoga, or engage in relaxing pastimes such as walking in the woods, soaking in a hot bath, or listening to music to establish feelings of calmness. Uncontrolled eating is often a response to stress.

▶ Keep up your guard. Track your weight, choose healthy foods over junk foods and smaller portions over larger ones, and try to tolerate hunger and resist cravings as much as possible.

▶ Get seven hours of good quality sleep each night. Sleep deficits are associated with increases in hunger.

▶ Be patient. Slow, steady weight loss is best. Focus on the long term. Expect occasional setbacks, and don’t let them discourage you: Simply resume healthy eating.

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