How Much Fat Can We Gain After a Massive Cheat Day?

How much weight can you gain in one day?

Let's begin with some good news; the extra weight you see on the scales isn't always body fat.

Fast-food meals generally contain lots of sodium, which brings lots of water into your cells and increases your total body water.

This can give the appearance (and a result on the scales) that suggest you've "gained fat." But what you've really only done is gain (water) "weight." 

The other issue here is carbohydrates, which behave similarly to sodium.

Carbohydrates are stored in our muscles and liver as glycogen, with every gram stored also bringing in 3-4 grams of water.

So, 200 grams of carbs can store 600 grams of water, which can yield about 0.6 extra grams on the scale. But consume nearly double that and it's about one kilogram; enough to freak most people out in a short time!

So don't get too bothered over carbohydrates and sodium intake, that number on the scales will disappear as the days go on (providing you return to normal eating patterns). 

Gaining body fat after a large meal

It happens; it's holidays, your birthday, Christmas, or any momentous celebration, and you overindulge. 

Ok, so what's the damage?

Well, this study fed 16 male subjects 50 per cent more than their maintenance level of calories for two weeks.

At the end of the study, they gained 1.4 kilograms of fat.

Not that bad considering they were bingeing for 14 days!

But what about the fat they gained after one day?

Well, the 1400 extra calories they consumed daily translated to roughly 90 grams of fat each day.

So, nothing to duck off to the bathroom to cry about!

Another study recruited 29 slightly overweight men and had them eat 40 per cent more than maintenance calories for 8 weeks.

They ended up consuming around 1200-1500 extra calories per day.

They finished up gaining 4 kilograms of fat, which translates to 0.5 kilograms per week, or 70 grams of fat per day.

So, we're looking at around 70-90 grams of fat from a big binge (and obviously more if we exceed a 1500 calorie surplus). 

Another study yielded interesting results; 15 healthy and physically active (30 minutes per day three times per week) men and women consumed a whopping 78 per cent extra calories over maintenance for one day (6000 calories per day as opposed to their normal intake of 3,350 calories per day). 

And this study was different in the sense that 60 per cent of the total calories were from fat.

So, what did they find? 

They gained about 0.7 kilograms of fat.

Thermogenesis and gaining less fat

The other factor to keep in mind is that thermogenesis plays a huge part. Thermogenesis refers to how many calories your body burns in the process of having to create heat to digest it. 

Let's take a look:

Protein: 30% rate of thermogenesis.

Fat: 0-3%

Carbohydrates: 5-10%.

So, if we're having a big eating day with the majority of our calories coming from fat, we're likely to store more body fat due to its lower rate of thermogenesis.

But consume more carbs, and the resulting body fat gains should be less.

And not that you'd consume lots of calories from protein on a day you want to go all out, but this study gave trained subjects an 800-calorie surplus from protein powder for 8 weeks, and they gained no body fat at all!

A calorie is indeed NOT a calorie.

We're all human. If we plan on having a day like this every month where we gorge excessively, it's not going to "ruin" weeks of dieting provided we get back on track. 

Various hurdles face us along the way, but if we can get back on the bandwagon quickly, we won't have anything to worry about.

The issues come when we maintain an eating schedule like this for weeks and months on end; that's when problems start.

The bottom line is that a 1000-1500 surplus of calories for a day means you'll only gain about 0.70-112 grams of fat. The scales might say you've gained more, but that's because of the water weight excess sodium and carbohydrates bring along with it. But boost that number up to 2000-3000 calories for a day, then you might gain around 0.22 kilograms. 

But remember to do it for one day only; any more than that obviously means more fat will be gained. The calories we consume make a difference too; prioritise your calories from carbohydrates, as they have a much high rate of thermogenesis (5-10%) compared to fats 0-3%.