5 Reasons It’s Nearly Impossible to Keep Weight Off

Suzie Glassman

Why our biology fights weight loss and what to do about it


How many times have you tried a diet, lost weight, and then found yourself gaining the weight back (and possibly then some) within a year or two? If it hasn’t happened to you, you’ve likely seen others struggle with losing weight only to gain it back. Up, down and up again.

It’s easy to think there’s something wrong with you (or someone you know) or with the diet. Is it a lack of willpower? Or perhaps your love of carbs is the enemy? As of February 2019, the weight loss industry totaled $72 billion. That’s insane. If diets worked, you’d lose weight once and never need to diet again. It’s perhaps the only industry that profits when its products fail and you have to repurchase.

Traci Mann, UCLA associate professor of psychology and lead author of a study on whether or not diets work in the Journal of the American Psychological Association, explains,

You can initially lose 5 to 10 percent of your weight on any number of diets, but then the weight comes back. We found that the majority of people regained all the weight, plus more.
Sustained weight loss was found only in a small minority of participants, while complete weight regain was found in the majority. Diets do not lead to sustained weight loss or health benefits for the majority of people.

There are dozens of theories as to why weight regain is inevitable, but there’s no question when it comes to keeping weight off, our biology is working against us. Here are five reasons biology is a frenemy and what to do about it.

1. When You Lose Weight, You Burn Fewer Calories

You may already know your metabolism slows down when you lose weight. While it’s frustrating to think you’re being punished for shedding extra pounds, there’s a biological reason this happens.

To understand metabolism, you first have to look at how we burn calories throughout the day.

  • By far, the greatest amount of energy expenditure (50–70%) comes from our resting metabolic rate (RMR). This is the number of calories we consume to keep the lights on (breathing, pumping blood, etc.). Muscle burns more calories at rest, so it pays to have a lot of lean body mass.
  • The thermic effect of food, which refers to the calories required to digest what we eat and turn it into energy, accounts for 5–10%.
  • The rest comes from our physical activity. Most of this activity is from walking, chores, working, and non-exercising functions. Exercise makes up a small portion of the total. Think about it — we may workout for an hour, but most of our day is made up of activity outside of formal exercise.

When you lose weight, your smaller self needs less energy to live. Your RMR declines as your body becomes more efficient and burns fewer calories than before you lost weight.

Second, your brain is incredible at adapting for survival. Our ancestors often went long periods without a reliable food supply, so we are hard-wired to conserve energy when food is scarce (like during a diet). Our metabolism becomes more efficient, allowing the body to survive on less energy than similar-sized bodies that were not calorie deprived.

This means that just to maintain our lower body weight, we need to eat less indefinitely.

2. Your Hormones Make You Hungrier

As if a slower metabolism wasn’t bad enough, our hormones start working against us when we eat less. Our brains begin pumping out more of the hunger hormone (ghrelin) and less of the satiety hormone (leptin) whenever we try to reduce the amount of food we eat.

In fact, leptin is released by fat cells and basically tells our brains when to eat and when to stop eating. When dieting, our fat cells release less of it, and we get a sense that we are starving, even when we aren’t.

Stephan Guyenet, Ph.D., author of The Hungry Brain, calls this a classic starvation response. Your brain responds by upping hunger, making those chips in the pantry call out your name, and ensures cravings are all but impossible to ignore.

3. Food is More Rewarding

In her research, Mann found that calorie deprivation also led to changes in a variety of cognitive and attentional functions such that dieters became preferentially focused on food.

A classic study called the Minnesota Starvation Experiment looked at conscientious objectors to WWII who volunteered to be semi-starved for six months and found the subjects spent much of their time talking about foods, planning future meals, reading cookbooks, and even considering new careers in food-related fields.

Side note: the participants ate 1,560 calories per day, which was considered a starvation amount. How many of us try to get by on less as a matter of routine these days?

Brain imaging studies also find increased activity in reward-relevant areas. Other studies find that when calorie deprived, people have improved smell functioning and report food tastes more palatable and are willing to work harder to earn it.

There’s a reason that chocolate bar tastes so good after depriving yourself all week or month. Your brain lights up more than it would if you weren’t calorie-deprived, and you may end up eating far more than you intended.

4. Some Scientists Believe We Have a Weight Set point

While controversial, some studies point out that our bodies have a weight range hardwired into our DNA. Go too far below this weight range, and your biological systems kick in to return you to your normal weight.

Mann told the Washington Post,

I don’t think people should try to live at a lower weight than their set range. If you try to lose weight so that you’re below your set weight range, that I believe is folly, or farce. It’s not healthy. It’s what sets off all those biological changes that are effectively trying to defend your set range.
When your body goes lower than your set range, it makes changes to bump your weight back into it. And what people don’t know is that if your weight goes above it, it also makes changes to push it back down into the ideal weight.

In Mann’s book, Secrets from the Eating Lab, she explains our set point can fall within around a 20-pound plus or minus range, and we should aim to live at the low end of our set point. Unfortunately, it’s far easier to raise our setpoint than to lower it.

I have a five-pound range where my body is comfortable. I can eat mostly what I want, exercise regularly, and enjoy a robust social life without gaining weight. To get below this weight, I have to get strict with my diet and limit nights out. To go above this weight, I have to stop exercising and spend a good deal of time eating excessively.

Experts say it’s possible to lower your setpoint by losing weight slowly, but for the most point, you should aim for a healthy weight and not one that leaves you having to count every calorie you ingest for the rest of your life.

5. Your Emotional Health Doesn’t Change With Your Weight

Many people believe the key to their happiness lies in reaching an ideal weight — one where he or she likes what they see in the mirror. The problem is that even if you reach that weight, you still have all the same problems you had before the diet. Or you may find you pick apart your flaws regardless of your size.

For many, guilt over wondering why they aren’t magically happier leaves them eating to cope with their feelings, which leads to a destructive cycle.

An article in The Atlantic explains how an extensive 2011 review of different weight-loss methods by Anthony Fabricatore, an assistant professor of psychology at the Perelman School of Medicine at the University of Pennsylvania, found,

While extensive lifestyle modifications in dieting and exercise produced the greatest improvement in symptoms of depression, there was absolutely no correlation between an improved mood and weight lost. In fact, nearly all the interventions, including those that didn’t focus on weight loss, had a similar effect.

If you feel better after losing weight, it may be exercising and eating healthier foods provides a larger mood boost than the weight loss itself. In that case, you’ll want to continue your new healthy habits. On the flip side, if you don’t feel any better after putting yourself through a rigorous diet, there isn’t much motivation to keep the weight off.

What to Do About All of It

Having made it this far, it may seem like there’s no point in even trying to shed excess weight in the first place. However, there is a percentage of people out there who lose weight and never gain it back. What should you do?

  1. Avoid an overly-restrictive diet. You’ll need to make changes you can live with long-term because you’ll need to stick with them over time. When you have a long list of prohibited foods, you’ll find yourself craving them more and more. The reward system in your brain lights up when you see them, and they’ll be much harder to avoid.
  2. Maintain your exercise routine. NPR states that according to the National Weight Control Registry, a database of people across the U.S. who have lost at least 30 pounds and have kept it off for at least a year, the №1 thing they have in common is they report exercising one hour every day.
  3. Lose weight slowly. You are less likely to kick off biological alarm bells in your brain if you cut calories by relatively little (300–500). It might take longer to lose all the weight, but it will be easier to maintain once you do.
  4. The best diet is the one you can maintain. Research shows it doesn’t matter whether you go low-carb or low-fat; both diets resulted in weight loss. What mattered most is that you stay with it for the long-term.
  5. Address emotional/life triggers. If you are constantly criticizing the image in the mirror, you may need professional help to learn how to love yourself as you are. Losing weight may not change your inner monologue. Also, address life stress to avoid binge eating. While we can’t avoid stress altogether, we can find coping mechanisms that don’t involve food. Meditation, walking, chatting with a friend, talking to a therapist, reading a good book — any number of practices can relieve built-up tension in your body.

Let go of blaming yourself for lack of willpower when your hormones are fighting against you. Biology might not be our friend when it comes to weight loss, but we can make positive lifestyle changes that improve our health and help us live to a ripe old age.

Comments / 0

Published by

I write about health and fitness with the goal to help you live a healthier, happier life.

Denver, CO

More from Suzie Glassman

Comments / 0