If there's one single thing that shocks and scares my clients and athletes, it's when I tell them to have a cheat meal.
Yes, I, a dietitian, encourage my dieting athletes to go out and have a burger on the weekends. It goes a long way in helping one maintain a healthy relationship with food and remember that eating is supposed to be an enjoyable experience, not an anxiety-inducing one.
However, can you gain weight by overdoing it or underestimating your intake?
Technically yes, but not in the way that you’re thinking. For anyone who has weighed themselves just a little too often…
(by the way, stop doing that. Once every other week is more than enough)
…you’re familiar with the confusion and discouragement you feel when you seemingly gained 3 pounds overnight. However, this weight gain is pretty much never body fat, unless your night out consisted of you literally chugging olive oil by the bottle.
So then why is the scale so unreliable? How long does it actually take to gain fat and what is the best way to track progress? Let’s investigate.
How Much Fat Can You Gain From a Day of Overeating?
I wish more people knew the science behind the answer to this question.
One of the biggest things I seek to accomplish in my work as a dietitian isn’t altering people’s weight, but their relationship with food. And the ridiculous idea that you can gain fat from one day of deviating from your diet makes people needlessly afraid of food which turns meals into an anxiety exercise rather than what it should be – a comforting experience of satisfaction.
So, let’s take a look at this study, which had adult males eat 50% more calories than they needed each day for two weeks. When the study concluded, the men only gained about 0.2 pounds of fat.
After 2 WEEKS of overeating.
Another study showed similar results, with nearly 0.2 pounds of fat gained per day after two months of overeating by 40%.
I get it. Most people have the common sense to not overeat by such a large margin for two whole weeks. Of COURSE you know what’s going to happen.
But think about it this way. You’d have to be trying really hard to overeat by 2 weeks. So if the weight gain was that marginal after 2 weeks of intentional overeating, how much weight do you think you’ll realistically gain after 1 day of accidental overeating?
I’ll let you work that out on a scratch sheet of paper at home. But I think you already know the answer.
So, Why Do I Weigh So Much the Next Day?
If you’re reading this right now, I’d be willing to bet you’ve had that sinking feeling of stepping on the scale after a weekend of holiday eating or a night of fast food binging only to see you went backwards.
By like a lot.
But I have an answer for you. Actually three answers: fluid, carbs and sodium.
The most obvious thing to acknowledge is that, if you drank more fluid than normal on a certain day, you may weigh more. Water adds many more pounds to your body weight than you may think, so keep that in mind.
If your overeating came in the form of foods you don’t normally eat like pizza, fast food, or restaurant food, you probably ate a ton of sodium. This is also true of certain cuisines like Asian or soul food that may use a lot of salt-based seasonings.
The thing with sodium is it makes your body retain water, which is why you may also notice some bloating along with a bigger number on the scale. This is what makes people convinced that they gained fat because it looks like they gained weight, too.
But it’s all water. Typically, it takes 2-3 days after the meal in question for your body to purge this water and your weight will normalize, but that doesn’t help your panic attack after taking your weight, which is exactly why we’re having this conversation.
What many people don’t know is carbs can have the same effect as sodium which is why many people blame carbohydrates for their weight gain. It’s also the reason why, when people go keto or low carb, they lose weight insanely fast. It’s because carbohydrates (look closely at the name…”hydrate”) carry water molecules with them as they travel through the body, especially when they are stored as glycogen in the muscles.
When people cut carbs, the body doesn’t hold onto nearly as much water as it usually does, so you look lean (ahem, dehydrated) and you lose weight (ahem, water weight). This is also why when people reach their goal weight on keto and go back to their regular, carb-filled diet, they gain their weight back.
And this is because they never lost any fat to begin with. All they did was shift the water in their body around.
How Much Would You Need to Eat to REALLY Gain a Pound of Fat?
Let’s work this out quickly. In the studies we talked about, the subjects gained only 0.2 pounds of fat after overeating by 1,000 calories per day.
This is a typical cheat meal, by the way. So if you’re petrified of indulging in a weekly cheat meal, I hope you have my voice in your head.
Anywho, the USDA assumes most Americans need 2,000 calories everyday to maintain their weight. So let’s use that as an example.
Your resting metabolic rate is 2,000 calories and you’re eating in a 500 calorie deficit, meaning you eat 1,500 calories per day on your diet. Then you go on vacation to, like, Vegas and go crazy. In one day on the strip, you stop by Shake Shack after the long travel and you are RAVENOUS. You order:
2 Double Shackburgers from Shake Shack - 1,520 calories
Bacon Cheese Fries from Shake Shack - 840 calories
Loaded Chocolate Cookies & Cream Shake - 1160 calories
A 32 ounce beer - 420 calories
Then you gotta stop by M&M World before the shows. To keep your blood sugar up, you pick up 6 pouches of peanut M&Ms, totalling 1,500 calories.
Then you eat your regular 1,500 calories for the day. For those who are savvy at math, you know this means, once you subtract the 2,000 calories you burned at rest, you overate 5,000 calories in Vegas. So, if you remember the study from before (yes, more math), you’d gain a total of 1 pound from these shenanigans.
However, if you took a look at that spread up there, you would need to try SO HARD to make that happen. It’s not just a result of grabbing an extra cookie at the company picnic.
And even if you did…one pound of body weight is hardly something to lock yourself away over if you’re following a solid diet and exercise regimen.
Better Ways to Track Your Weight Progress
As you can see, the scale isn’t always a reliable way of accurately tracking your progress, mostly due to how easily and quickly water retention and fluid shifts can tack on (or take away) pounds and pounds of weight.
Given that this doesn’t give you a good picture of how much fat you’re losing, this can result in discouragement and can cause you to cut further calories when you probably don’t need to. Not only can these derail your progress, but you’ll be just…so sad.
So, consider cross referencing your weight data by taking other measurements that are not as easily influenced by external factors such as:
Waist circumference
How pants and shirts fit
How you look in the mirror first thing in the morning
How strong you feel
How much energy you have
Taking before and after photos
It’s also important that, when tracking weight, you make sure conditions are the same each time. For example, it’s not a good idea to weigh yourself at night when your last weigh in was in the morning or to weigh yourself in a track suit when you usually weigh yourself in your undies.
It's also generally a good idea to weigh yourself first thing in the morning after you have emptied your bladder and bowels and before you have eaten or drunk anything.
You should also know that, especially if you’re at the very beginning of your journey and are drastically changing your lifestyle, weight will not behave as you may expect. For example, I often see new clients who are just starting weightlifting and increasing protein intake start to go up in weight dramatically and they freak out.
This is why I encourage them to measure their waist and take note of how their musculature looks in the mirror because this weight gain is almost always muscle and they have lost a good amount of fat, but it’s impossible for the scale to make that distinction. This is why these alternative metrics of progress are vital.
The Bottom Line on How Much Weight Can You Gain in One Day of Overeating?
It appears that most people who overeat by about 1,000 calories, which is about the amount of a Big Mac meal, you’ll likely only gain ⅕ pound of fat. Meals like this also tend to be high in sodium, so the next day it’ll look like that McDonald’s trip set you back a few pounds, but now you know that’s not the case and this is just water retention in action.
It is therefore crucial not to weigh oneself regularly, as in every day, as some people do.
Once every other week is more than enough and mixing in other metrics of progress never hurt to give a more accurate picture.
So, no, you didn’t gain “like 5 pounds” from that night out with your friends, but also – don’t get sloppy people. The purpose of this article was to put at ease the minds of people who beat themselves up after enjoying an impromptu burger and even punish themselves with hours of exercise.
It’s just not necessary.
However, don’t take advantage of how realistically forgiving the body’s metabolism is. If you overeat on a consistent basis, there’s no more blaming “bloating” or “water weight” – you will gain fat in significant amounts.
And if your diet quality is bad, meaning you’re eating a lot of pizza, doughnuts and ice cream, this can even rob you of your muscle gains and put you at risk for chronic diseases like heart disease and type 2 diabetes.
So, the takeaway is… please enjoy your cheat meals. We all deserve a mental break from being diligent throughout the week and to reward ourselves with something indulgent so we don’t find ourselves binging out of deprivation. Just don’t go crazy.
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