How Much Weight Can You Gain in a Day?

Limit to Calories Converted to Fat?

Standing on a scale
There's a limit to the amount of weight you can gain in a day, no matter how much you eat. nensuria/iStock

Have you ever wondered if there is a limit to how much weight you can gain in a day, no matter how many calories you eat?

Calories and Gaining Weight

Now, if you do the math, you need an excess 3500 calories to put on one pound of fat. Keep in mind, a pound of fat translates into more body weight because you gain water weight in addition to gaining fat. Given that your stomach can only hold so much food at a time, there is a practical limit to how many calories you can consume in a day.

If that day is Thanksgiving, for example, you're actually filling up on some foods that aren't incredibly high in calories. You're eating a combination of food, not just pure fat, which would be your quickest route to high calories. This means it's unlikely you'll intake more than 10,000 calories, no matter how determined you are to feast until you can't eat any more.

That translates into a couple of pounds, at most, because you're burning calories while you're consuming them. If the meal is high in sodium, you may retain additional water weight, but you'll shed that over the next couple of days, assuming you return to your normal eating habits.

There's a Limit

Another factor to consider is that you only produce a certain amount of the enzymes needed to digest your food. Now, don't delude yourself into thinking you'll meet that limit with a normal large meal, but there is a limit to how much of any nutrient you can process and absorb.

You also have your metabolism to consider. If you severely restrict calories, your metabolism adapts so you can burn them more efficiently. Eating too many calories can have the opposite effect, revving up your metabolism as part of a physiological process to maintain a 'set point'.

Whether you can alter your metabolism with a single day's change is debatable, but even competitive eaters don't necessarily gain weight.

If you do gain weight, most of it will be water and fat, since it takes time to add more muscle mass. Also, keep in mind you can increase your metabolism on your own by increasing your activity level.