What you need to know about “overnight” (short-term) changes in body composition

I used to be afraid of getting too muscular. I didn’t want to be a lump of bodybuilding sludge, unable to scratch my back. I always wanted to be sleek. Like a ninja.

So when my friends (all four of them) and I played multiplayer video games, I always was the small quick dude. GAUNTLET. The elf. I was never the slow clunky barbarian.

gauntlet nes

Funny. The dude that always was the clunky barbarian is huge now (muscularly). Pretty sure he does steroids, too.

people share similar thoughts, only they take them one step further.

i don’t want to get too muscular… OVERNIGHT.

the same “overnight” concept bleeds into muscle loss and fat gain, too.

I didn’t train — oh no! — I don’t want to lose all all my muscle overnight!

I need to slim down my holiday dinner, I don’t want to get fat overnight! 

common thoughts.

that need smeared with shit.

brushing up on energy balance

in order to put these short-term body composition changes into perspective, let’s talk about energy. specifically, energy balance.

if you haven’t read my collection of farticles on energy balance, click here. the TL;DR being: your body uses energy every second of every day, and you eat energy every day to stay alive.

the amount of energy you eat is measured via calories. The standard example, the reference point, always seems to be 2000 calories. in other words, you need to eat 2000 calories every day to maintain your current weight.

the 2000 calorie thing is 100% not accurate for 99.9% of humans, but, for the sake of this conversation, and to avoid more percentages, and commas, let’s assume that it is. you need 2000 calories every day. if you eat this amount, you stay the same weight.

Mediocristan and Extremistan

this 2000 calories, the energy you need in order to maintain yourself, exists within a Mediocristan domain. perhaps the best way to understand a Mediocristan domain is to first understand an Extremistan domain.

(FYI, I’m stealing the concepts of Mediocristan and Extremistan from Nassim Taleb. Consider this a paralagiarismphrase of ideas that appear in The Black Swan.)


in an Extremistan domain, one instance or output can greatly unbalance the average. so imagine lining up 1000 middle class people and finding their average income.

chances are, the largest deviation from the average won’t be HUGE. and, if you added another middle class person into the lineup, the average wouldn’t change much.

but now imagine throwing Bill Gates into the lineup. suddenly, with Gates, the largest income deviation from the average IS huge. and thus, the average changes immensely.

this is Extremistan in a nutshell.


in a Mediocristan domain, one instance or output can’t greatly unbalance the average. so imagine lining up 1000 people and finding their average body weight.

just as before, the largest deviation from the average won’t be huge. and, if you added another person into the lineup, the average wouldn’t change much.

but here’s the difference…

even if you now add the largest living human into the lineup, the new adjusted average still won’t change that much… even if s/he weighs three or four times the initial average.

this is Mediocristan in a nutshell.

what WON’T happen overnight

as mentioned, your energy intake exists largely in a Mediocristan domain, meaning one single input (day) won’t have a devastating consequences on the extended average.

meaning none of these things

  • losing a meaningful amount of fat
  • building a meaningful amount of fat
  • building a meaningful amount of muscle
  • losing a meaningful amount of muscle

will happen overnight, even if you use the most EXTREME measures possible. you can play this out with numbers.

you can’t lose fat overnight

assuming you need 2000 calories every day to maintain your weight, that means you’d eat 60,000 calories in one month.

even if you starved yourself and ate nothing in one day, you’re not greatly affecting the overall monthly average intake.

  • all days @ 2000 = 2000 daily average
  • one day @ 0 = 1933 daily average

to put these numbers into some perspective, the rule of thumb is that one pound of body fat “contains” 3500 calories. in other words, even if you did the most extreme thing possible (starved yourself for the day), you wouldn’t lose one pound of fat.

you can’t get fat overnight

likewise, even if you ate as much as you could in one day, you (probably) wouldn’t greatly affect the monthly average calorie intake.

“probably” is in parenthesis because there’s greater deviation potential when it comes to overeating.

when you starve yourself, there’s a bottleneck: zero calories. when you gorge, the bottleneck is your stomach’s capacity to hold food.

in today’s age, food is hyper palatable, flavor enhanced, and calorie dense — designed to hack your satiety circuitry. you might be able to eat, say, 10000 calories in one day.

  • all days @ 2000 = 2000 daily average
  • one day @ 10000 = 2266 daily average

this has a bigger affect on the monthly average calorie intake. given a pound of fat “contains” 3500 calories, it would seem as if you gained two pounds of fat overnight.

but the body isn’t a nematode.

the meat sweats

if you slurped up 10000 calories in one day when, usually, you only eat 2000 calories, it seems as if you’ve consumed +8000 calories. but the body isn’t static and linear. the numbers wouldn’t shake out like that.

ever have the meat sweats? you eat so much food, your body temperature jacks through the roof? when you eat more food, your body burns more calories.

in other words, you wouldn’t really be +8000. granted, you’d still end up with a calorie surplus. but it wouldn’t be as severe as +8000.

numbers dawg

you might still be wondering… “Well, even if it is +5000, I’ve still gained a pound of fat though, right?” meh. maybe. probably not though.

this world of numbers we’ve created in regards to how our body functions is nice and all, but there are a lot of things we have no quantifiable frame of reference for.

for instance, your daily metabolic rate is tied to your bodyweight. so if you did gain a pound of fat, you also have to assume your metabolic rate changed ever so slightly which BUTTERFLY EFFECTS OMFG I DON’T KNOW WHAT I’M TGALKINGB BOUt

feelings, undereating and overeating

screw the numbers. what about feelings? if you chucked back 10000 calories in one day, you’d certainly wake up the next day feeling fatter, right?

absolutely. but the feeling wouldn’t actually be a byproduct of gaining body fat. most short-term feasts make you feel fat because:

  1. You have a bunch of food sitting in your stomach, which makes you feel bloated.
  2. Your feasts also contain high sodium foods, which means you’re retaining more water than you normally do.

Both of these make you feel (and look) softer and puffier. typically, a day of two of “regular” eating will autocorrect this feeling.

similarly, when most people don’t train for a day (or a week) and feel less muscular, they aren’t really losing muscle. the feeling is a byproduct of short-term adaptations, like your body carrying less muscle glycogen — something that will also autocorrect after one or two training sessions.


in the end, your body won’t make meaningful metabolic adaptions in 24-hours. it just so happens that both body fat and muscle mass fall under the “meaningful metabolic adaptations” umbrella.

if you want to lose fat, it takes more than a day EVEN IF YOU DO THE MOST EXTREME THING POSSIBLE AND STARVE YOURSELF; if you’re afraid of gaining fat, it takes more than a day EVEN IF YOU DO THE MOST EXTREME THING POSSIBLE AND GORGE YOURSELF.

if you want to gain muscle, it takes more than a day EVEN IF YOU DO THE MOST EXTREME THING POSSIBLE AND STRENGTH TRAIN NON-STOP; if you’re afraid of losing muscle, it takes more than a day EVEN IF YOU DON’T MOVE A SINGLE JOINT. 

your body composition is a product of trends, not fads.

your body isn’t Yikes pencil, is what i’m saying.

Trying to lose fat, build muscle, and build a body you’re proud of?

Maybe you’re a little lost right now.

Maybe you don’t have much motivation.

Maybe you don’t what program or diet to use.

I don’t know…

But what I do know is this:

Everything you need is inside of you.

You’re capable of more than know.

You just have to open your eyes.

My weekly column can help.

Just a small little honest note from me sent every Sunday.

Unless I’m hungover.

And then it comes Monday.

What I’m trying to say is that it’ll come Monday.

(These weekly columns don’t get posted to the site.)

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