This is for the people who are a tad obsessive about eating right. It's for the people who go to a holiday potluck and bring something like a keto, crustless kale pie to pass around; the same people who emerge from the sumptuous buffet line carrying nothing but a plate of gravy-less turkey and a sliver of keto, crustless kale pie.
I have a message for you: Gather ye crab puffs while ye may. Life is short. Old time is still a'flying and all that. But aside from paraphrasing a famous Elizabethan poet, I want to tell you that pigging out in a single meal, or even several meals over a short period of time, isn't going to do diddly to your body fat percentage – or at least not much diddly.
Zero Net Fat Accrual
I previously wrote about a study where scientists fed a group of healthy men a single meal of bread, jam, and fruit juice that totaled 480 grams of carbohydrate (about 1,900 calories), about 8 grams of fat (about 70 calories), and a smattering of protein. The scientists then tracked their metabolic responses for 10 hours.
The bulk of the carbohydrate was converted into glycogen (346 grams) while the rest of it (133 grams) was burned as fuel. It's true that their bodies converted some of the carbs to fat through a process called "de novo lipogenesis," but it was only a measly 2 grams.
However, during the 10-hour follow-up, the subjects BURNED 17 grams of fat. That's 7 grams more fat than the combined total of what was in the meal (8 grams) and the fat they manufactured through DNL (2 grams), so they burned an additional 7 grams of body fat after the meal.
So the gross overfeed led to zero net fat accrual.
But what happens when you eat meals that are really fatty, pig out all day long, or, as often happens during holidays, pig out for several days straight?
A Fat Loss Ceiling?
Oddly enough, a couple of studies seem to indicate a fat gain "ceiling." They found that regardless of how many calories subjects ate in a single day, whether it was 2,000 calories beyond maintenance or 5,000, it only resulted in a fat gain of about 0.2 pounds. Check it out:
- A University of Colorado study involved 16 people who were fed 50% more calories than what was required for maintenance. This continued for two weeks. Each subject gained about 0.2 pounds of fat a day.
- A study at the Pennington Biomedical Research Center involved 29 men were fed 40% more calories than maintenance every day for 8 weeks. They each gained about 0.2 pounds of fat a day.
But another study, this one conducted at Loughborough University, took 15 normal weight individuals and fed them 78% more calories than needed for maintenance over the course of a SINGLE day and the average "weight gain" was 1.76 pounds.
That's a hell of a lot more than the 0.2 pounds discussed above, but fat gain isn't the same as "weight gain," is it?
Most Weight Gain From Humungous Meals is Transient
Make no mistake, you do gain weight after a pig-out meal, but the added weight is unlikely to be fat, or at least any substantial amount of fat, especially if the meal or meals is a rare occurrence or limited to a short period (like a one-week vacation).
In more concrete terms, you could gain a pound of fat if you eat an extra 500 to 1000 calories a day for a week, but not if you eat an extra 500 or 1000 calories in a single meal.
For one thing, there's a limit to how much food your body can turn into fat via de novo lipogenesis (DNL) in one sitting. And even if that meal is extremely high in fat, there's that apparent and mysterious (at least to me) fat storage ceiling of 0.2 pounds that I spoke of.
But beyond that, there are several things that determine how much weight you gain when you dive into the horn of plenty with a couple of shovel-sized spoons. The good news is that all of them are associated with transient weight gain, meaning that if you're just patient, the vast majority of the weight you gained from your dietary excesses will disappear on its own accord.
The first determinant is carbohydrate intake. A small amount of carbs is turned into fat via DNL, but much of the rest of the ingested carbs are stored as glycogen in the liver and muscles, and along with each gram of stored carbohydrate comes about 3 grams of water.
The amount of "soggy" glycogen stored varies enormously from one individual to another and may be particularly large in weightlifters, athletes, or muscular people in general, especially if they've worked out that day (thus depleting glycogen to a certain degree).
Then there's the extra sodium that's intrinsic to any large meal. Eat enough of it, and your body turns into something that's more water balloon than human. Add that to the extra water associated with all the stored glycogen and it could add up to 5 or 10 pounds of fluid.
Lastly, there's that slow-moving freight train of waste moving through your large intestine and colon. It can represent a couple of malodorous pounds all on its lonesome.
The good news, as stated, is that most of that extra weight is "false" weight and temporary. Do nothing and it will mostly disappear in a few days. After all, the average weight gain from a week or even two of holiday bingeing is somewhere around 1 measly pound, not 10 or 15.
So have a ladle-full of that streuseled sweet potato casserole and a dollop of that creamy shrimp piccata. Lean back, unbutton your pants, and rest easy in the knowledge that most of the weight gain from those holiday feasts is temporary.
- KJ Acheson, et al. Glycogen synthesis versus lipogenesis after a 500 gram carbohydrate meal in man," Metabolism, 1982, Dec 31 (12):1234-40.
- Jim Schwarz, et al. "Short-term alterations in carbohydrate energy intake in humans. Striking effects on hepatic glucose production, de novo lipogenesis, lipolysis, and whole-body fuel selection," J Clin Invest 1995, Dec;96(6):2735-43.
- Alex Leaf, "Can one binge make you fat?", Examine.
- Alex Leaf and Jose Antonio, "The Effects of Overfeeding on Body Composition: The Role of Macronutrient Composition – A Narrative Review," Int J Exerc Sci, 2017, 10(8).
- TJ Horton, et al. "Fat and carbohydrate overfeeding in humans: different effects on energy storage," Clin Nutr. 1995 Jul;62(1):19-29.
- Darcy Johannsen, et al. "Effect of 8 Weeks of Overfeeding on Ectopic Fat Deposition and Insulin Sensitivity: Testing the 'Adipose Tissue Expandability' Hypothesis," Diabetes Care, 2014, oct; 37(10):2789-2797.
- Francis Mason, et al. "Effectiveness of a brief behavioural intervention to prevent weight gain over the Christmas holiday period: randomised controlled tria," BMJ, 10 December, 2018.