Why it’s hard to maintain weight loss

About 70% of U.S. adults are trying to lose weight. However, as a result of evolutionary pressures dating back to our most distant ancestors, our bodies are programmed to resist weight loss. 

Michael Rosenbaum, MD

Research by Michael Rosenbaum and others has shown that losing weight and keeping it off are different. And keeping weight off is harder. 

“We are richly endowed with genes that defend the storage of calories as fat,” says Michael Rosenbaum, MD, professor of pediatrics and medicine at Columbia University Vagelos College of Physicians and Surgeons, who studies how our bodies fight weight loss.

Early humans were subject to frequent periods of poor access to nutrition. People best at storing fat calories when food was available, and conserving them when it wasn’t, were most likely to survive and reproduce. “Evolutionary pressures favor genes that enhance reproductive capacity, and the ability to store calories would clearly meet this criterion,” says Rosenbaum. “The tendency to gain weight and the difficulty in losing it and keeping it off is primarily a biological problem, not a reflection of sloth and gluttony.” 

Your body’s weight loss battle

Rosenbaum’s research with his Columbia colleague Rudolph Leibel, MD, and many others, has shown losing weight and keeping it off are different. And keeping weight off is harder, often requiring a lifetime of attention. Contrary to popular opinion, people without obesity generally have just as much difficulty in sustaining a small degree of weight loss as people with obesity have with even larger degrees of weight reduction.  

During weight loss (usually by diet) and weight loss maintenance, multiple biological systems “conspire” to return us to our previous levels of fat stores to maintain the passing down of calorie-storing genes. After losing weight your metabolism is likely slower and your appetite is likely greater and will probably stay that way if you keep the weight off.  

To keep weight off you must actively work to address, and hopefully reverse, the biological changes induced by weight loss. But what’s the best way to do that?

Rosenbaum is currently trying to find out by looking at the regulation of body weight from "the lowly fat cell to the highest cortical centers of the brain” in a much more meticulous way than previous studies. 

The key question is: Can we identify the reasons that make weight loss hard for each individual and design personalized approaches that make it easier?  

Each person has different degrees of slower metabolism and increased appetite and different reasons that make it hard to maintain weight loss, says Rosenbaum. By looking for the genes, biological markers, and behaviors that have the biggest effects in each person, researchers can design more focused interventions to address individual differences. “There are no assumptions that one approach will work for everyone, but there are a lot of reasons to believe that we can design the best approach for anyone,” he says.  

Body weight is important to health

Many people are concerned about weight. Unfortunately, says Rosenbaum, we tend to define successful weight management based on appearance, not health. “Even a small amount of sustained weight loss can have tremendous health benefits, and anyone who achieves this should be supported and admired," he says.

Healthy habits that keep weight off 

The National Weight Control Registry follows over 10,000 individuals who have sustained weight loss. In this group of successful weight loss maintainers: 78% eat breakfast every day; 75% weigh themselves at least once a week; 62% watch less than 10 hours of TV per week; and 90% exercise, on average, 1 hour per day. That said, there is no one-size-fits-all program. “If there were universal things to do that worked for everyone, we would be doing them,” says Rosenbaum.

avocado salad on a plate

Most weight regain is attributable to eating more, rather than moving less, so diet should be a major focus, says Columbia obesity researcher Michael Rosenbaum. Photo: Getty Images.


Rosenbaum recommends: 

  • Find what works for you.
    • Some people do best with a low fat diet, some with a low carb diet, some with intermittent fasting, and some will need to switch regularly.  
  • In general, diets should be balanced and healthful, minimizing ultra-processed foods and high fructose corn syrup. 
  • Exercise regularly. 
    • Aim for less screen time and more “move around” time—even if it is just walking around the room while watching television. 
  • Do not compare yourself to others or what works for them.

The only scientifically proven weight loss tips are: eat less and move more. However, notes Rosenbaum, just stating the laws of thermodynamics ignores the tremendous physiological opposition to doing it. Some people may be able to lose weight and sustain weight loss with exercise, but most weight regain is attributable to eating more, rather than moving less, so diet should be a major focus.  

Whatever you do, Rosenbaum says, do it safely and with input from a health professional.  


Michael Rosenbaum, MD, is professor of pediatrics and medicine at Columbia University Vagelos College of Physicians & Surgeons and associate director of the Clinical Research Resource at the Irving Institute for Clinical and Translational Research at Columbia University Irving Medical Center.