The Key to Losing Weight
In medical school, we were taught that controlling weight was as easy as doing math in elementary school: subtracting calories from food equals losing weight. Eat less, move more, problem solved.
Therefore, why have obesity rates continued to rise, reaching 40% of Americans in 2021 and 2023? It’s because our brains evolved to resist weight loss and prefer high-calorie foods during times of scarcity. This makes today’s food environments, where shelves are filled with highly satisfying food, extremely problematic. The more we reduce our calorie intake, the more loudly our brains urge us to consume more, and we’ve all got a ready supply.
Recent research Does that mean we’re all doomed? We are not, according to a study that was recently published in Nature Medicine. Its findings add to the growing body of evidence that the missing piece is changing what we eat rather than focusing so much on how much we eat. Dr. Dicken and his team presented the findings of a randomized clinical crossover study that was conducted on 55 overweight people who routinely consumed more than 50% of their calories from ultra-processed food (UPF). Participants were randomized to either an ad libitum UPF diet or a minimally processed food (MPF) diet; after eight weeks, participants were switched to the other diet. All meals, snacks, and beverages were provided to participants on both diets, which adhered to UK nutritional guidelines. While both diets were matched in nutrient levels and maximum energy intake (4,000 kcal/day, though participants could eat less), the MPF diet was associated with significantly more body weight loss (2 percent) than the UPF diet (effect size of 0.5), in addition to more fat mass loss and reduced triglyceride levels.
In other randomized trials where calorie consumption was not controlled, similar separations between the MPF and UPF diets on body weight were documented. By what mechanism did the MPF diet promote weight loss in this study? Primarily, it made people eat less. On average, the MPF diet reduced participant calorie intake by 170 more kcal per day than the UPF diet did.
Why do diets rich in whole foods cause people to eat less?
For one, whole foods are less energy-dense than UPFs. When you eat, you stretch receptors in the stomach, which makes you feel full through the activation of the vagus nerve. This signals the brain to integrate with signals from neurohormones like leptin to change how you eat. Highly rewarding foods with lots of fat and sugar inhibit vagus nerve activation and reduce the desired inhibitory effects of eating.
Second, despite a greater weight loss, participants on the MPF reported a decrease in cravings and a decrease in “hedonic appetite,” which refers to an appetite that is primarily motivated by pleasure seeking. UPFs are engineered by the food industry to be more rewarding, and often contain high levels of sugar, which can fuel hedonic eating.
The same brain circuitry that drives the use of nicotine, alcohol, and other drugs of abuse also controls hedonic eating. Similar to other addictive substances, excessive consumption of high-sugar processed foods results in long-term changes in emotional, cognitive control, reward, and motivational circuits. As a result, it becomes increasingly challenging for individuals to exercise control over their consumption of these particularly rewarding foods.
Does quality win over quantity when it comes to weight loss?
One thing is becoming increasingly apparent—food quality matters because it alters our brains—despite the fact that there is a great deal to be learned about how to best address obesity and addictive eating. Better choices are more likely to come from what we eat.
