Why Calorie Restricted Diets Don’t Work

Dr. David Ludwig
4 min readNov 19, 2015

According to the USDA’s Choose MyPlate website, “Reaching a healthier weight is a balancing act. The secret is learning how to balance your ‘energy in’ and ‘energy out’…” A secret, indeed! In reality, no one, not even nutrition experts, can accurately “practice” calorie balance. Without elaborate technology, it’s virtually impossible to estimate to within 350 calories a day how much we eat and burn off. A calorie gap of that magnitude can mean the difference between remaining thin and developing morbid obesity in just a few years. For that matter, if counting calories were key to weight control, how did humans manage to avoid massive swings in body weight before the very concept of the calorie was invented?

Cutting back on calories will cause weight loss for a while, which gives the illusion that we have conscious control of our weight over the long term. However, many bodily functions are within our temporary, but not permanent control. For example, many people can lower the amount of carbon dioxide in the blood for several minutes by breathing fast, but few can do so for much longer.

Researchers have actually known for decades why conventional diets don’t work over the long term, although this knowledge has been generally disregarded. When we begin to cut calories, the body launches potent countermeasures designed to prevent additional weight loss. The more weight we lose, the more forcefully the body fights back.

In a classic series of studies dating to the 1980s, investigators at Rockefeller University in New York underfed volunteers to make them lose 10 to 20 percent of their weight, and then studied their metabolism during lengthy admissions to the research unit. Regardless of whether the participants had normal or high body weight at the beginning of the study, they experienced a large drop in metabolic rate — far more than could be attributed to weight change alone. And of course, underfeeding made the participants hungrier.

These findings explain an experience all too familiar to anyone who has been on a diet. When you eat fewer calories, the body becomes more efficient and burns fewer calories, even as your desire for extra calories heightens. This combination of rising hunger and slowing metabolism is a recipe for failure. After a few weeks of calorie deprivation — long before our weight loss target is within sight — we become tired and tempted to quit our exercise routine, and collapse on the couch with a pint of ice cream. If we marshal a Herculean effort, stick to the diet, and stay active, metabolic rate will continue to fall, so we’ll need to cut calories even more drastically to kept losing weight.

The body’s weight control systems also work in the other direction. When volunteers are forced to gain weight by overfeeding under carefully monitored conditions, their metabolism speeds up and they tend to lose all interest in food. After the period of enforced feeding ends (to the relief of the volunteers), weight typically drops quickly back down to each individual’s usual level.

In fact, it’s difficult for anyone to change body weight significantly in either direction. Just as a heavy person would struggle to lose 50 pounds, so would a lean person struggle to gain 50 pounds. For both over- and under-eating, these biological responses push weight back to where it started — to a sort of “body weight set point” that seems largely predetermined by our genes. If you inherited obesity genes from your parents, the biological responses that defend body weight will kick in for you at a higher range compared to someone who didn’t inherit those genes.

We’ve been following the wrong advice for too long. Dieting doesn’t need to be this hard. The key to long-term weight loss isn’t counting calories; it’s eating in a way that lowers insulin levels, calms chronic inflammation and, by so doing, readjusts the body weight set-point to a lower level. That is the focus of the program in my forthcoming book, Always Hungry. You won’t count calories on this program. But you will eat well — including luscious high-fat foods (like nuts and nut butters, full-fat dairy, avocados, and dark chocolate), savory proteins, and natural carbohydrates — until you’re completely satisfied. It’s dieting without deprivation.



Dr. David Ludwig

Physician, Nutrition Researcher, and Public Health Advocate. #1 NY Times bestselling author ofALWAYS HUNGRY? and ALWAYS DELICIOUS