Why You Gain Weight on Diets (And The Simple Fix)

Why is it that most diets cause weight loss followed by a period where you gain weight? It’s a mystery that leads most people to believe that the entire diet industry is a hoax.

While there are many (many) bad diets that can easily be blamed for why you gain weight, most diets are designed to work. We know this because people lose weight and can keep it off. So what, then, causes the big divide between those that keep pounds off and those that gain them back?

The answer is something known as “set point theory,” which probably means nothing to you. But if you’ve ever found that you gain weight when you diet, it’s likely the missing piece of the puzzle that can change everything.

If more people understood that plateau is a part of weight loss, then they wouldn’t quit prematurely.

Long-Term Weight Loss Is Real (But You’ve Been Fooled)

I’ve been journaling–somewhat consistently–since second grade. While unpacking boxes after a recent move, I found an entry from 1991 (I was 9) that read: “I don’t have to always fit into big pants.”

I was that guy. The chubby guy who needed his pants tailored for his Bar Mitzvah because they didn’t make suits for young men with a waist so big and height so… restricted. 

If my story sounds cliche, well, it is. But it’s not too good to be true. The part missing from the fast-forwarded version is that I struggled with weight loss (and the dreaded weight loss plateau) and body image for years. I’d go as far as telling people I was allergic to chlorine to keep my T-shirt on in the pool. (I’ll never understand how I thought this explanation would work. It’s not like the shirt protected my skin from the water, but I digress… )

My ultimate success was a byproduct of many (many) failures and learning how to overcome times of despair and lost hope. I shifted away from gimmick diets and “four-week plans” and focused on blocking out my negative thoughts and becoming happier with who I was. Then I could finally focus on the other part of the weight-loss battle: building a realistic plan for my body.

It’s the same approach I’ve used to coach hundreds of overweight people to better health and fitness and more happiness. But it all starts with believing a simple truth that is starting to feel more like myth than reality: You can transform your body. Most people just do it the wrong way. Too fast. Too impatient. Too generalized. And too unrealistic.

I’ve worked with clients who have lost 100 to 200 pounds.  And most of the time, these successes happen over the course of months (or even years), not five episodes on a television show. At least, that’s the case for those who successfully keep the weight off.

This is an especially important point because some research (and recent media coverage) suggests that long-term weight loss is hopeless.  While many people do, in fact, gain weight they previously lost, it’s not because dropping fat is “mission impossible.”

Instead, it starts with changing your definition of “success,” setting aside instant gratification, and understanding how weight loss actually works. When that happens, everything changes and anyone can build a plan that ensures they’re not another sad statistic.

Why do you really gain weight?

First, some bad news: All nutritional approaches or diet plans stop “working” at some point. Weight loss stops. You don’t see changes, and you believe that either you or the plan are no longer functioning. The good news: When it appears to stop working, it’s actually still working.

Confused? Stay with me and it’ll make more sense.

We know that as you lose weight, your metabolism tends to slow down–although it’s not absolute. (This research reviewed 71 studies and didn’t find a significant drop in metabolism.) We also know that if you’re patient about (focus on losing one to two pounds per week at most), then you’re more likely to keep it off for good. But most people quit before significant weight loss occurs. It usually looks something like this:

Step 1: You lose weight (sometimes, a lot, and very fast)

Step 2: You stop losing weight

Step 3: You’re still not seeing any changes.

Step 4: Weight gain.

Step 5: You’re pissed off, frustrated, and quit.

This process usually happens in less than 6 weeks. If you believe some studies, the average person diets for an average of 6 weeks — followed by 14 weeks “off” a diet. That’s not a good balance of results.

The thing is — and what no one tells you — steps two and three (stalled progress/plateau) are often an important part of the weight-loss process.

Dropping one to two pounds per week is considered healthy, but it’s also the average. That means you might lose four pounds one week and zero the next. On those weeks when the scale doesn’t change, it’s not necessarily a sign that your body has reached its weight-loss limit.

To put it another way, your plateau is a  necessary part of the process. You must stall in order to move forward (again). And when you understand why–or, more importantly, accept this reality–it changes everything.

The Only Real Weight Loss Secret

Your body does not like change. I don’t care who you are; it’s very resistant to anything that takes it out of its comfort zone (a.k.a. homeostasis). When that change occurs–specifically when you try to lose weight–your body does everything in its power to adjust and get you “back to normal.” This is a process known as set point theory.

If you ask me, set point theory is the reason why so many people fail on long-term weight-loss goals. If more people understood that plateau is an expected and natural part of the process, then they wouldn’t quit prematurely. Sometimes the scale isn’t moving simply because your body is adjusting to change.

Here’s how it works:

We all have a “normal” body weight. Whether we like that weight or not is a different story, but this is the weight that we’ve come to “accept” as our own. We also have a look we desire, whether it’s your college weight, your pre-baby body, or where you were that one time you got super fit a few years ago.

Your mind wants to achieve your goals, but your body wants to cling to what’s familiar. So when you try to change, physiological reactions occur to suck you back into the body you’ve known for so long.

The more weight you lose, the harder your body works to resist that change, or even pull you back to your old weight. It does this by slowing your metabolism (comparatively) and increasing your hunger. Sucks, right?

Just wait, it’s not all doom and gloom. If you can hang in and resist the urge to quit, these changes are temporary and can help ease the permanence of your weight loss.

Set points are not carved in stone. It’s more like frozen in carbonite, a la Han Solo. You can undo the process by changing your body and allowing your body to adjust. This is why plateaus can be so deceiving. Your body is adapting to its new reality. Once it does, that’s when you’re ready to take the next jump and see a “whoosh” of new weight loss.

Everyone’s set point is a little different, so there’s not one rule for how long you have to wait. The more weight you have to lose (say, more than 50 pounds), the quicker it can happen initially without hitting your set point. If you want to lose closer to 15 or 20 pounds, you might hit a wall after the first 10.

This is why you’ve seen so many magazine cover lines about “How to Lose the Last 10 Lbs.” Those should really say, “How to Be Patient After You Lose the First 10 Lbs.” But that doesn’t sound as sexy.

Once you hit your set point, your body likely needs anywhere from four to eight weeks to adjust to your new weight. Then you’ll establish a new set point, and your body will respond like that’s your new normal.

It doesn’t sound that exciting, but it’s better than you think.

If you go from 200 to 180 pounds or 150 to 130 pounds and wait out the set point process, your body’s drive to move back to the old weight has changed. It becomes much easier to stay at your current weight because your body no longer thinks it’s outside its comfort zone–and you’re able to start losing weight again. On the flip side, it becomes much harder to gain weight, as well.

The result: you don’t feel like you’re constantly following a pain-in-the-ass plan. That’s why long-term fat-loss never occurs in 30 days or anything magical. It’s a process.

Finding the right eating approach is about seeing the long-game. Almost any plan can deliver the quick results. Ignore those. Instead, focus on what you think you can do for six to 12 months. When you do, you won’t be as frustrated when you hit the set point. Instead, you’ll be buying time–not buying a new approach (literally)–until the weight loss starts again.

READ MORE: 

Winning the War on Hunger: Practical Solutions to Overeating

Fix Your Diet: Understanding Proteins, Carbs and Fats

Big Meals vs. Small Snacks: What’s Best For You?