A diet culture favorite: Burn what you eat
By Trần Thy Vân 7.1
“I’m being so unhealthy today, but that’s fine; I’ll just burn off the calories in this later!” Someone said, as they ate an entire tub of ice cream. The following day, they restricted calorie intakes and ran miles on an empty stomach to compensate for the ice cream. Upon returning home, they step on the scale anxiously, praying that a larger number wouldn’t appear. However, much to their disdain, it went up by a kilogram. Staring at the number, they wonder why their run didn’t “eliminate” the ice cream they had.
A popular belief among diet culture and “fitness influencers” nowadays is that you can “burn what you eat” to maintain a certain weight. However, life’s complicated—and so is your digestive system.
Water retention
The human body isn’t a machine or math equation—so don’t expect it to behave like one. Similarly, although you (hypothetically) ate and burned the same amount of calories, your body weight still added up. Could it be that you gained a kilo of body fat? No, you didn’t—but rather water weight (edema). Your body stores excess water or fluids as water weight, a condition known as water retention. While water retention is made up of a number of factors, we'll focus on high carbohydrate intake regarding the ice cream catastrophe.
If you paid attention during 7th grade science, you’d know that when we eat carbohydrates, our body converts them to glucose for immediate use. According to Medical News Today, the energy from carbohydrates that we don’t use right away is stored away as glycogen instead, and each gram of glycogen carries 3 grams of water. So, the next time you freak out about how your body didn’t “burn what you ate,” ask yourself: Did I eat an extra 7700 calories yesterday, 1100 extra every day for a week, or is it simply water retention?
2. Metabolic adaptations:
When plants are forced to grow in a shady environment, they adapt traits such as wide, dark leaves to absorb as much sunlight as possible. The dark color provides high chlorophyll concentration, while wide leaves help increase surface area for sunlight. Similarly, when you exercise excessively to “cancel calories” or restrict yourself, your body slows down metabolism to preserve energy as a survival instinct. This causes you to burn fewer calories as you work out, contradicting the idea of “burning what you eat.”
A PubMed Central report says, “Reductions in sympathetic nervous system, thyroid hormones (thyroxine), and insulin maintain low energy expenditure, acting like defense mechanisms against further weight loss.”
3. CICO proven wrong:
The idea of “burning whatever you eat” is generally based on the “calories in, calories out” weight loss model, otherwise known as CICO. CICO suggests that weight management relies solely on how much you eat and burn, which downplays the complexity of our digestive system. It ignores the caloric quality and macronutrients, thus driving doctors and researchers to challenge its reliability.
According to Professor Giles Yao, a molecular geneticist, not all calories are equal due to the energy required to digest and metabolize them. Different macronutrients have distinct biological functions, which influence how we process and use energy.
In conclusion, the idea of “burning what you eat” oversimplifies how your digestive system works as a whole. Although this diet culture ideology is scientifically correct, it is incomplete due to factors such as water retention, metabolism, or macronutrient differences. At the end of the day, I'm not here to dictate your life choices, but if you’d rather listen to diet culture’s values rather than research done by professionals—who am I to stop you?
