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John Tjepkema of Orono is a professor emeritus in the School of Biology and Ecology at the University of Maine.

Many people make a New Year’s resolution to lose weight. They may have greater success if they and their advisors take advantage of two recent advances in knowledge. One is that while exercise is not a significant factor causing the obesity epidemic, it is important as part of weight loss. The second is that many of our modern foods have effects on the brain that are similar to addictive drugs and cause us to overeat. Such foods were not common 100 years ago, and obesity was also not common.

Reduced exercise has been proposed as a major cause of the obesity epidemic. However, even though we are much less active than hunters and gatherers or subsistence farmers, we actually expend the same number of calories per day per unit of body weight. Greater physical activity is compensated for by using fewer calories for other metabolism, such as the immune and stress response systems. These may be overactive in those who exercise less. Thus reduced exercise does not appear to be the major cause of the obesity epidemic. Nonetheless, studies of those who have maintained weight loss for long periods find that they exercise more than normal weight controls.

Much of the food that we now consume is processed and has multiple ingredients. Food manufacturers and restaurant chains do extensive research to make their food as appealing as possible. It is now known that processed foods act on the brain via the same reward circuits that addictive drugs act on. Foods high in both refined carbohydrate (such as sugar and white flour) and fat are especially appealing, and strongly activate the reward system. Appeal is further increased by adding flavorings, colorings and optimizing texture and salt content. Such foods may also require little chewing and are fast to eat. All of this leads to overeating compared with the foods available 100 years ago.  

Diet trials indicate that the key to weight loss is the elimination from our diet of at least some of the foods that cause us to overeat. Major weight loss has been achieved using a wide variety of diets. These include keto, paleo, native Hawaiian, vegan, elimination of ultraprocessed foods and a diet consisting entirely of a sugar-containing balanced nutrition drink. These diets were all ad libitum, meaning that the subjects could have as much as they wanted and were not hungry. What the diets have in common is the elimination of foods that overstimulate the reward center of the brain. It appears that one can lose weight with many kinds of diets as long as the diet is sustainable for the long term.

Food manufacturers and restaurant chains are very much aware of how their products lead to obesity. However lawsuits have not been successful in forcing them to make any changes in their products. Taxes on some types of food and soft drinks can have an effect. 

Public education may have greater potential to help with weight loss and in the prevention of weight gain. The key messages should be a moderate amount of exercise and elimination or limitation of foods that overstimulate the reward center. In addition, suggestions of alternative foods are essential. These can be based on individual preferences. The balance between fat, carbohydrate and protein can vary, as well as the source of protein.

For success in limiting obesity on the national level, some of the tactics used to break away from tobacco, hard drugs and other addictions may be useful. I encourage members of our congressional delegation to investigate possible legislation. Federal support for educational efforts seems feasible, as has been done for tobacco and drugs.