The next logical question that comes after I show how EASY it is to overshoot your needs by 1000+ calories, especially on a holiday weekend:
What happens in my body if I totally blow my macros?
While overeating *might* cause some level of fat gain (research shows you could add .1-.3 pounds of body fat when you overeat your needs by 1000 calories), there are several changes taking place in your body that reduce the number of calories that are actually stored as fat.
you burn more calories to digest more food
Digestion accounts for approximately 10% of the total calories you burn in a day. That is, about one in ten calories is spent simply digesting your meals. Eat more, burn more calories digesting.
The size and composition of your meal determines the changes in metabolism.
Protein has the highest thermic effect of food (TEF) at around 30%, carbohydrates have a TEF of 5-10%, and fat has a TEF of 0-3%. So overeating your needs with protein technically “burns” more calories via digestion when compared to carbohydrates and fats.
you store more or less as body fat depending on the macro
Overeating your calories does not mean those calories all get stored as body fat – it also depends on the percentage of those calories are coming from each macro.
Protein is used almost entirely for repairing, building, and regenerating cells, hormones, and other molecules in the body, and the excess is burned off as fuel in the liver. It’s almost never directly converted into body fat. Carbohydrate is mostly stored in the liver and muscles as glycogen. It is stored as body fat over a few days of overeating because carbohydrates have to undergo a very different energy-intensive process to be converted into body fat. Fat is chemically similar to the kind of molecules stored in body fat cells, so your body prefers to store dietary fat as body fat and prefers to burn carbs for energy needs instead.
you may move more when you eat more
… just like you may move less when you eat less.
Activity levels change when you overeat. Research shows that some people will spontaneously and subconsciously move more throughout the day when they overeat. This extra movement is known as non-exercise activity thermogenesis (NEAT). NEAT varies a great deal from person to person. However, the average increase in energy expenditure from NEAT activities is about 300 calories per day, higher in men than in women.
you don't absorb every calorie you eat
Some foods, particularly ones high in fiber like grains, nuts, seeds, whole fruits and vegetables often make their way through the digestive system without being completely broken down. What’s more, these high-fiber foods can also interfere with the absorption of fat, meaning more fat gets excreted in BMs.
No, this doesn’t mean that those extra cheat day calories just go in one end and out the other – it just means if you consume more than you need, no doubt there will be higher fiber content in your diet that day. You may excrete a few more calories from fat in your poo.
So, if you’re in a position where you’re definitely going to overeat your needs, it’s almost always better to do it with protein containing foods.
A review of the of the most current scientific literature showed that even chronic overfeeding (up to 16 weeks!) with 800 more calories from protein did not result in body weight or body fat gain when compared to overfeeding from a mixed macro diet. Check out the review PMID: 29399253
The body has plenty of functions for protein. It’s simply not efficient to digest, absorb, and repackage those molecules as body fat.
