Why science says pigging out for a few days won’t damage your waistline as much as you think
You can already smell the panic. The week-long binge fest that we call Christmas is approaching. You know there’s nothing you can do to avoid the inevitable fat gain. According to research, the fat gained over Christmas hangs on after the festivities. In fact, it represents more than 50% of the weight gained throughout the year.
I know. Oh my god.
To the regular Joe, it’s no big deal. But for the fitness junkie, this calls for drastic measures.
You concoct various fasting regimes or periodise your diet with low and high days. All in the hope to make it out the other side and into January unscathed. But do you need to bother?
What happens when you binge? How much weight do people actually gain? In answering these questions, you can see if you’re making a fuss for a good reason or not.
Let’s take a look at the science of short-term overfeeding.
Fat or water?
Ever woken up the day after a massive blow out and noticed you were 5kg heavier? Fat gain right? Well, not quite.
Fat tissue isn’t only made of fat. Water and protein are both abundant. 1 kg of what we’d consider fat contains roughly 7,559 to 8,254 calories. Did you eat 38,000 to 41,000 Calories more than usual the day before? Didn’t think so. As I’ve written about before, most of that weight is increased water due to a higher than normal sodium intake. In a few days, you’ll be pretty much back to normal. Phew. So how much fat can you gain over one day?
Fidget or sloth?
There’s no getting out of gaining fat when you’re in a huge Calorie surplus. Even if it’s only one day. The question is, how much fat will you gain?
Remember that thin, fidgeting kid from school? You know, the one whos knee fidgeted under his desk like a pneumatic drill? It turns out that some people become this guy when you overfeed them. And this is not anecdote. In a study by Levine et al. some people almost burned off their 1,000 Calorie surplus by moving around more. The kicker is, some people in that study actually moved less when overfed! With the same increase in Calories, what makes some people fidget more, and others fidget less? The answer might be genetics.
In 1990 a study by Bouchard et al. overfed 12 pairs of identical twins 1,000 Calories over maintenance for 100 days. They gained an average of 8.1 kg, of which 67% was fat. Here’s the interesting bit. The lab coats found large variation in how people responded to the extra Calories. This variation was not random. The identical sets of twins stored similar amounts of fat, and also stored it in the same place.
What this shows us is that it’s down to your genetics. You might not actually have much real control over how much fat you store. Or where you store it.
This doesn’t mean to say that some people can’t gain fat while other people look at a mince pie and put 5lbs on. A calorie surplus over time will result in fat gain for anyone, regardless. Some people just have a helping genetic hand where packing on the pounds is concerned.
”Screw genetics! How much fat can I actually expect to gain if I smash it for a week?”
I’m getting to it! Ok, let’s have a look.
Real world weight gain
We know that you can gain weight no matter what, but the amount you gain might be down to genetics. But, what can you actually expect from less than 2 weeks of hardcore pigging out? Anecdotes aside, there isn’t actually much literature looking into this. And you can’t look only at weight gain. You need to see how much of that weight was actually fat.
But, if you get your geek on, you can find some clues.
The following is a quick rundown of decent overfeeding studies lasting a realistic 2 weeks or less.
- Had 5 young men in a 60% Calorie surplus for 9 days
- The average weight gain was 3.2kg, with 56% of it being actual fat
- Had 9 lean and 7 obese men in a 50% Calorie surplus from fat or carbohydrate for two weeks
- The lean subjects gained 1.09kg from carb overfeeding and 1.21kg from fat overfeeding. 54- 56% of the weight was actual fat
- Had 11 men and 14 women consume an extra 20 Calories per kg body weight from either candy or peanuts
- That works out as an extra 1,500 kcal for a 75kg person
- Body weight increased 0.8kg in the candy group and a measly 0.3kg in the peanut group
- Excuse me while I smash 1,300kcal of dry roasted…
- Had 7 men and 2 women consume 4,000 Calories a day for 2 weeks
- They limited their activity to 1500 steps per day (a bit like at Christmas)
- They gained an average of 2.4kg in body weight.
In all 4 of these studies, the most actual fat gained was 1.8kg from 9 days in a 60% surplus. To put that into perspective, if you maintain your weight on 2,500kcal, you’re looking at eating 4,000kcal a day for 9 days. You can deal with that amount of fat gain within a week or two of structured dieting if you need to.
I don’t know about you, but I’m thinking this isn’t a big deal.
Let’s sum up what we’ve learned so far:
- Weight gain is rarely ever only fat gain
- If you put a tonne of weight on the next day after overeating, it’s almost not all fat unless you ate 40,000kcal the day before
- Overfeeding studies prove you don’t turn into the Mr Creosote if you go hard for a couple of weeks
I know you care about Instagram selfies and six packs. You’re all about the “fitness lifestyle” and that’s cool. But, don’t lose perspective. Unless you’re going to go mental, you aren’t going to do much damage to your waistline with a short-term surplus.
Relax and enjoy yourself.
If you’re getting stressed out, consider re-thinking your plan. Put that diet, fast, or any other silliness on hold in the run-up to Christmas. One day, three days, or two weeks aren’t going to make much difference in the big scheme of things.
Want to lose weight while still going out to eat the foods you love? Get the eat out stay lean system and never worry about eating out again.