Why Most People Who Lose Weight Will Gain It Back

Losing weight, especially a large amount, is hard. It takes determination, a drastic change in lifestyle, and Jillian Michaels screaming in your face.

OK, that last one's not true, but you do need to literally work your ass off. Finally reaching your goal may feel like a success, the end of the road in a long journey, but it's only half the battle. The toughest part is keeping it off. 

"We know that 90% of people who lose a lot of weight eventually regain it," says Dr. Eduardo Grunvald, program director at UC San Diego's Weight Management Program. It's one of those health facts that's become conventional wisdom -- like how drinking lots of water is great for you, and food is more important than exercise for weight loss -- but most people aren't sure of the exact science behind it. 

It turns out that it's more than just people reverting back to old habits; there are some depressing medical reasons why your body is inclined to put back on the weight it lost. Despite the various forces working against you, losing weight isn't a lost cause. Here's what's really going on with your body when you lose a lot of weight, and how to keep it off for good.

Diets are temporary by nature

A big trap most people fall into is thinking that diets are a short-term fix to a long-term problem. They follow a specific plan until they hit their goal, then eventually fall back into the old patterns that made them fat in the first place. This is a recipe for disaster. 

"Willpower usually doesn't work for the long term," Dr. Grunvald says. People tend to have razor-sharp focus when they first start losing weight, and are motivated as the numbers on the scale keep dropping each week. Especially with an end goal in mind -- a goal weight, an ideal dress size, a major event like a wedding or class reunion -- it's easy to rely on self-control and determination to get you through your weight-loss journey. But once you reach your goal, then what? That's when people start to fall back into their old habits, and watch the weight creep back up.

"It's [about] taking that comprehensive approach," he says, adding that changing your overall environment and lifestyle with a focus on the long term will give you those lasting results. "At the end of the day, it's about making healthy choices. You can try and make it easier for yourself, or you can just use willpower by itself, which doesn't work."

Your hormones betray you

When you shed pounds, it's more than just your outside appearance that changes; inside, your body is making a dramatic shift. Sadly, it's not in your favor.

"As you start losing weight, the hormones in your body that regulate your weight change, so that appetite and cravings are actually stimulated in your brain," Dr. Grunvald says. "Some of this is subconscious, but as you lose weight, you are driven to eat more."

Perfect. Just as you're getting your junk-food habits under control, your brain plays tricks on you to make you want entire meals of chips, cookies, and pizza again. If it's hormones, there's NO WAY TO STOP THE CRAVINGS, right? Fortunately for you and your teenage self, you're more than your hormones -- being aware that your brain is playing tricks on you is a good first step, but if you need help combating cravings, check out these simple, yet effective tips

Your metabolism fights back

You'd think your metabolism would adjust to your new, fitter body, and work in your favor to help you burn calories. Unfortunately, like your hormones, the complete opposite happens. 

"As we lose weight, our metabolism slows down, and it's not just because you're losing weight," Dr. Grunvald says. "The metabolism slows down even more than you would expect just for the loss of mass. That's a concept called metabolic adaptation, so basically it's your body slowing down metabolism even further than it should."

The Biggest Loser study that was published earlier this year exemplified this phenomenon, where most of the contestants who lost a lot of weight gained it all back... and then some. The problem was simple math; contestants had a much slower metabolism after they lost so much weight in a short amount of time, so they actually needed to eat less than a person of the same size to maintain their new weight. Basically, a formerly fat person doesn't burn as many calories as a person who weighs the exact same amount, but was never fat.

After the finale, Season 8 winner Danny Cahill gained more than 100lbs of the 230 he lost, and even at this weight burns 800 calories less than the average man his size. Your metabolism actually wants to keep you obese.

So how am I supposed to keep the weight off for good?

Maintaining weight loss is more complicated than simply continuing the habits developed to drop the weight in the first place. Dr. Grunvald prefers to think of obesity as a chronic disease -- one that needs to be treated and cared for over a lifetime. 

"Diet and exercise usually isn't very effective in the long term, and I think it's because it's a very difficult thing to do, it's an even more difficult thing to maintain," he says. "No matter what you do, the minute you stop doing it, it's going to relapse." 

Keeping off the weight you lose requires always thinking ahead to the future. "We know that for most people, if you don't take an intense approach and a long-term approach, then you tend not to be successful. And that's the big challenge in obesity management, is really the long-term maintenance."

The biggest indicator if someone is going to keep off their weight loss is their environment and support system at home. That means more than having a partner who says, "Looking good!" when you wake up -- it has to be the total package, people who will eat healthy meals with you, keep your kitchen free of junk food, and join you on your trips to the gym. 

Sure, losing a bunch of weight in the first place is hard enough. Why worry about hypothetically gaining back all of the weight in the future? But with the right attitude, and a comprehensive approach to the long term, it's totally doable. Even with those damn ice cream cravings. 

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Christina Stiehl is a Health and fitness staff writer for Thrillist. She's a former professional yo-yo dieter. Follow her on Twitter @ChristinaStiehl.
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