Why You Won’t Gain the Weight Back

Part I: Why You Won’t Gain the Weight Back

You probably did a double take when you saw the title of this post. After all, everyone knows that the majority of dieters gain the weight back. That’s every dieter’s worst fear, and the reason that I limited myself to 1300-1500 calories per day for about a month after successfully losing weight last winter.

But when I finally started raising my calories—to 1800, then 2000, then 2400, a strange thing happened—I didn’t gain the weight back (you can read more about this here). And if you do it right, neither will you—regardless of what your family, your friends, or the media might tell you.

So why is this? Well, it boils down to one simple principle:


This might sound obvious, but a lot of people don’t fundamentally get it—which is why they don’t understand that eating “healthy” foods won’t automatically make you lose weight, that eating the same thing as your skinny friends won’t automatically make you their size, and (most importantly for this post) that the calorie intake you consume to lose weight is NOT equivalent to what you’ll have to eat the rest of your life to maintain that weight.

But losing weight means you’ll have to eat less now, right?

Well, yes. But the difference isn’t as dramatic as you think. I’ll use myself as an example: As a 21 year old, 5’8 female, at my starting weight of 160 lbs my BMR was 1572 calories. (BMR = Basal Metabolic Rate: the amount of calories you’d burn if you laid in bed all day; you can calculate yours here). At 140 lbs, my BMR is 1485—only an 87 calorie difference! Of course, I’m not actually lying in bed all day, so I have to multiply that by an activity level multiplier to find my actual calorie needs:

Harris Benedict Formula

To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows:

  1. If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
  2. If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
  3. If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
  4. If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
  5. If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9

We’ll say for the sake of illustration that I’m moderately active both before and after weight loss.  This means my daily calorie needs are 2435 before, and 2300 after—only a 135 calorie difference! To put that in perspective, that’s about the equivalent of a large apple. Or a slice of bread. Or a cup of yogurt. Or a single cookie. Hell, most people’s diets probably vary by 135 calories per day due to measurement error alone. Regardless, that’s still a LOT more than I was eating to lose weight, and at 2300 calories I’m certainly not going to feel like I’m on a diet the rest of my life.

For arguments sake, let’s say I misjudged and went back to exactly how I was eating before. I would be at a 135 calorie surplus so yes I would be gaining weight…but at that rate it would take me 74 WEEKS to gain the 20 lbs back (actually more than that, because my BMR would be increasing and therefore the surplus would also be decreasing as I gained the weight back). I’m sure that at some point along the line I’d notice what was up, drop back into a deficit, and quickly lose the 3-4 lbs I’d gained by that point.

And this isn’t even taking into account the effects of exercise. Let’s say that I was in fact sedentary at 160 lbs. My calorie needs would be 1885 per day, compared to 2300 per day at 140 lbs but moderately active…meaning that I could now eat 415 calories MORE per day while still maintaining a lower weight. And the more dramatically you’ve changed your eating and exercise habits to lose weight, the harder it’s going to be to simply revert back to those old behaviors.

Bottom Line: Yes you have to eat a LITTLE less after losing weight, but it’s not as big a difference as you think, and you certainly don’t have to eat at a deficit your whole life to maintain your weight loss.


So if it’s all so easy, why do diets fail? Why do most people gain the weight back, and then some? Why aren’t we all skinny? Here’s my thoughts:

1. You didn’t actually lose the weight in the first place

You know how when you first start a diet, you might “lose” 3 or 5 or 10 lbs in the first week? Odds are you didn’t actually LOSE all that weight—most of it is water weight. You’re on the right track, and your body will follow along, but the scale is always going to stay a couple pounds ahead (ie lower than your actual weight). That’s why someone who has JUST weighed in at 125 lbs today is going to look larger than someone who’s weighed 125 lbs their entire life. (You can really see this on the Biggest Loser, where contestants are dropping huge amounts of weight each week and tend to look larger than their scale weight would imply).

When you reach your goal weight, it’s probably going to take you several weeks to actually *look* that weight. If you increase your calories gradually up to maintenance, you won’t see the scale change, but you’ll be getting thinner as your body catches up to the scale. I’ll use myself as an example again—based on the calculations I did in part 1, my daily calorie needs were 2435 at 160 lbs and are now 2300 at 140 lbs. If I lost weight by eating 1500 calories per day, I might increase my calories each week to 1700, 1900, 2100, and finally 2300. Since I won’t see the scale move during this period I might THINK I’m maintaining at 1600, 1800, or somewhere along the line, but in reality my body is STILL losing weight at this deficit, and I’ll reach “true” maintenance at 2300. On the other hand, if you immediately start eating at your new maintenance level once you’ve hit your goal weight, the scale will likely jump up a few pounds right away. But that doesn’t mean you gained real weight—it’s just water weight that you never lost in the first place.

The more rapidly you lose the weight, the more dramatic this “bounceback” effect is likely to be. If you lose 10 lbs in ten weeks, the rebound will probably only be a pound or two, if at all. Whereas if you ‘“lose” 10 lbs in one week, it will all probably be back a week later. This is why fasting, crash dieting, and extreme low calorie diets are pretty much pointless—they’re not going to help you lose a significant amount of real weight.

But this effect only partially explains of weight gain. How do we explain people who gain ALL the weight back and then some? Well read on…

2. You Don’t Know How to Eat at Maintenance

Eating at maintenance to me is SO much easier than eating at a deficit. I mean, what’s not to like about eating more food? To maintain my weight, I don’t fundamentally change HOW I eat; I don’t eat differently—I just eat MORE: larger portions, more snacks, I don’t limit fruit, I always eat when I’m hungry, and I don’t necessarily track calories/macronutrients since I tend to naturally gravitate toward the ratios I’m looking for.

But most people don’t think this way. For most people, they’re either ON a diet or OFF a diet. “Dieting” means a long list of foods they can’t eat: no alcohol, caffeine, diet soda, sugar, white flour, bread, fruit, carbs, red meat, any meat, dairy, desserts, junk food, fast food, restaurant meals…whatever the diet of the week happens to be. If they eat any of these foods then they’re “cheating.” Chances are they’re also aiming for a unsustainably low number of calories EVERY single day, and engaging in behaviors that they’ll never be able to keep up: waking up at 4am to work out, eschewing all parties and social gatherings, packing 100 of their meals that they *must* eat at the same time everyday, and so on.

Now suddenly they’re “off” a diet, and their behavior changes 100%. They’re not just eating more; they’re eating totally differently, and going hog-wild on their favorite foods now that they’re no longer off-limits. And even if they’re eating on track MOST of the time, all it takes is a couple days of overeating to cause weight gain. Take for instance the common pattern of eating well during the week, then going crazy on the weekends. Someone with a binge eating tendency is especially prone to this because they could easily eat enough in two or three 60 minute binges to cancel out a whole weeks worth a eating normally or even at a deficit. So you might FEEL like you’re always on a diet even while you’re gaining weight. Or you convince yourself that you have to eat less than 1500 calories each day to maintain your weight, while conveniently ignoring the bi-weekly binges that bring your calorie average to well over 2000 (this was SO me in high school!) This also creates a vicious circle in which people undereat to compensate for a binge, yet undereating triggers another binge, and the cycle never ends.

Moreover, many people spend their entire LIVES cycling between going on and off a diet, and therefore have zero conception of what eating normal even means—there’s no benchmark or baseline to return to. Inevitably the off-a-diet periods will cancel out the on-a-diet periods, and weight gain results—often even more so than if they’d never “dieted” in the first place. Which brings me to…

3. Your metabolism is fucked

Most people take for granted that dieting slows their metabolism. Courtney at Barbells and Beakers does a really good scientific explanation of why this isn’t true. Yes, a temporary calorie deficit will lower your metabolism slightly, but if you return to eating at maintenance then there should your calorie burn should return too. (Especially if you lift weights to keep your metabolism up!) However, if you’ve been yo-yo dieting your whole lifs, your metabolism WILL get slower. Our bodies are smart and designed to be efficient at conserving energy. If your calorie maintenance level is 2200, but you force yourself to maintain at 1600, then eventually your body will adjust to operating at that level, and you’ll gain weight if you do go over. (Note: for a real-life testament to the benefits of eating more to keep your metabolism high, check out my story here.)

And if you eat at starvation levels for a long period of time, eventually your body WILL go into starvation mode and start holding onto calories. Model Crystal Renn’s story as recounted in her autobiography hungry is a perfect example of this: she dropped from 165 to 95 lbs at 5’9, then continued to starve herself and overrxercise to maintain this unnaturally low weight. Finally her body couldn’t take it any longer, and she started gaining weight. She went from 95 lbs to 130 lbs despite eating under 1000 calories and working out 8 hours a day, and jumped back quickly to 165 even once she started eating normally again.


And THIS is why diets fail. This is why people spend their whole lives gaining and losing the same 20 pounds. Or go start dieting to lose 10 pounds and wind up five years later and 40 pounds heavier. It’s not because losing weight is fundamentally impossible, or eating healthy is unsustainable, or because some people are just meant to be fat. If you gain the weight back, you’re doing it wrong. And chances are you’re doing it wrong in a way that makes your life harder, not easier.

So how do you avoid gaining the weight back? Just do everything I say 🙂 Seriously though, I’ve written out a blueprint on figuring out how much of every to eat that I think is a really useful starting point for losing and maintaining weight. The best-known name for this approach is IIFYM: If It Fits Your Macros, and it’s an incredibly flexible approach that can be adapted to any eating style and does not restrict/limit or mandate ANY foods. You can find my guide here.


4 Responses

  1. Shannon! Thank you for posting this. I recalculated my targets and I think it will make a huge difference! I skipped the step between BMR and accounting for sedentary activity, and wow…that explains why I’ve been so incredibly tired all day long on BMR + eating back the calories I burned with exercise.

  2. I ate a bigger breakfast today because of you, and that breakfast WASN’T a bagel!

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