05/01/2026
You’re tracking your eating and exercise meticulously but not seeing results. Has your metabolism slowed to a crawl? Are your hormones off? Is it really possible to GAIN weight from eating too LITTLE? Here’s what’s really going on—and how to solve it.
Truth: Thermodynamics don’t lie.
You’ve probably heard the phrase—the laws of thermodynamics—before. Or maybe you’ve heard it as energy balance. Or “calories in, calories out.”
Let’s break down what it actually means.
Thermodynamics is a way to express how energy is used and changed. Put simply, we take in energy in the form of food, and we expend energy through activities like:
basic metabolic functions (breathing, circulating blood, etc.)
movement (daily-life activity, purposeful exercise, etc.)
producing heat (also called thermogenesis)
digestion and excretion
And, the truth is…
Energy balance (calories in, calories out) does determine bodyweight.
If we absorb more energy than we expend, we gain weight.
If we absorb less energy than we expend, we lose weight.
This has been tested over and over again by researchers, in many settings.
It’s as close as we can get to scientific fact.
Sure, there are many factors that influence either side of this seemingly simple equation, which can make things feel a little confusing:
However, humans do not defy the laws of thermodynamics.
But what about unexplained weight changes? That time you ate a big dinner and woke up lighter? When you feel like you’re “doing everything right” but you’re not losing weight?
Nope, even if we think we’re defying energy in vs. energy out, we’re not.
And what about hormones?
While hormones may influence the proportions of lean mass and fat mass you gain or lose, they still don’t invalidate the energy balance equation.
Yet, it is easy to understand why folks get confused about this.
Stay tuned tomorrow for more about hormones and other factors.