It all comes down to calories.
If you burn more calories than you take in, you lose weight. If you take in more calories than you burn, you gain weight.
This is one of the immutable laws of thermodynamics and is commonly referred to as CICO or Calories In, Calories Out.
The next logical question is: how do our bodies do this? What self-defense systems do our bodies activate to slow weight loss, increase weight regain, and prevent future weight loss?
Metabolic Adaptation
Metabolic Adaptation (or Adaptive Thermogenesis), a set of physiologic changes, tends to be the reason most people stall in their weight-loss journey.
As you’ll see throughout this blog series, the body’s self-defense system is “persistent, saturated with redundancies, and well-focused on restoring the body’s depleted energy reserves.”*1
When we diet, the body’s main defense system to limit energy depletion is called “metabolic adaptation.” I’ll discuss metabolic adaptation in-depth in the upcoming articles, but essentially, it refers to a series of biological adaptations to energy restriction (aka dieting) that result in a slowing of metabolic rate to a greater extent than is predicted based on pure physics and math alone.*2
This is the defensive Department of your body’s self-defense system. It’s as if your body overreacts to dieting and slows your overall total daily energy expenditure (TDEE), more commonly known as your “metabolic rate,” and makes energy production in the body much more efficient to prevent further weight loss.
Metabolic adaptation includes, but is not limited to; the adaptations that cause a
decrease in your basal metabolic rate (BMR),
massive decrease in your non-exercise adaptive thermogenesis (NEAT, which I will cover in-depth in the coming articles),
alterations to your hormones including insulin, leptin, ghrelin, thyroid hormone, and others to a profile that decreases metabolic rate and increases hunger.
Almost anyone who has dieted has noticed that when they first start, it’s pretty easy to lose weight, but you don’t continue to lose weight at the same rate indefinitely. Indeed, weight loss slows down over time and eventually stops.
But why? If you were still eating the same amount of calories, shouldn’t weight loss continue?
Metabolic adaptation stops weight loss in its tracks, because what was once an energy deficit eventually becomes energy balance (calories consumed now equals calories expended) and weight loss stops unless the further restriction is imposed.
That’s not all. Your body also upregulates the systems that regulate fat deposition and increase hunger, so that eventually when you “finish” the diet or “fall off the wagon” and you eat more, you gain it back much faster and more efficiently than you lost it.*3
Even while you’re dieting, your body is already setting you up for regaining fat by activating systems in the body that improve the efficiency of energy storage which directs the increased energy (aka calories) you consume in the post-diet setting towards preferential fat regain.
Not only are you storing fat more efficiently during this initial “post-diet” period, but your hunger is also much greater due to lower levels of leptin, insulin, neuropeptide Y, as well as increased secretion of the hormone ghrelin which increases hunger.
These mechanisms drive you to not only increase your energy consumption (to eat more) but become more efficient at storing it so you regain fat much faster than you lost it.
If all of this was not bad enough, the body also has an enormous trump card that it can play to make energy storage more efficient.
There’s mounting evidence to suggest that if you regain body fat too quickly during the initial post-diet phase, not only can you regain body fat quickly, but you can add new fat cells.*4 *5
You see, typically your fat cells simply shrink or expand as you lose and gain weight. However, in an effort to defend your body against future starvation, it adapts by increasing the potential for energy storage.
This is the third department of the body’s self-defense system, the prevention department that makes it more difficult to lose weight in the future.
In this way, the body produces a massive and multi-faceted approach to slow/ stop energy depletion (and thus slow/stop weight loss), quickly refill energy reserves, and make it more difficult to deplete energy/body fat in the future by increasing the potential for energy/fat storage.
Dieting is not something to be taken lightly, and you need to do it and recover from it correctly. Otherwise, these diets will not only fail, but they’ll likely leave you worse off than you were before you ever began dieting.
Let’s try an example of a hypothetical dieter who follows this typical “yo-yo” diet cycle, and what impact that might have on their metabolism based on the available data.
If John has a metabolic rate that expends 2300 calories per day his Total Daily Energy Expenditure (TDEE), and he begins a diet that puts him at 1500 calories per day, his energy deficit is 800 calories per day.
(here is the fun calculation for losing 1kg in 1 week 🙂
With this deficit, he will lose weight. If he was 90kg / 200 lbs when he started, maybe he gets to 80kg/180 lbs before metabolic adaptation catches up to him and he finally plateaus at 80kg/180 lbs.
This means that 1500 calories per day are now his TDEE, and if John keeps eating 1500 calories a day, he will neither gain nor lose weight.
Maybe John is happy with this and decides the diet is done or that he can go back to eating like he used to. Or maybe John has some difficult life circumstances or stress and he “falls off the wagon.” Whatever the reason, John starts eating more, except now the research data suggests that Joe will eat more than previously because his hunger hormones will be elevated, causing what’s known as a hyperphagic response, which is well-documented in the literature
If John is eating 2500 calories per day because he’s so glad the diet is over or because he’s stress eating, which is common for many people, now he’s actually in an energy surplus of 1000 calories per day and will begin re-gaining weight rapidly.
In fact, the research data suggests he’s likely to blow past his original starting weight since his hunger hormones won’t likely normalize until he’s regained more than he lost. What’s more, these adaptations persist for years after the diet is finished in the case of people who lose massive amounts of weight.*6
John may end up weighing 95kg/210 lbs before his weight finally stabilizes and his metabolic rate returns to normal.
Moreover, if he initially regained some of that weight too rapidly, then he may have increased his total number of fat cells, making it more difficult for him to lose weight in the future. That and any subsequent weight loss will be even more likely to be short-lived and result in weight regain.
so the Solution is to get educated about the journey of fat loss either with an online coach or you can do this by yourself.
Just be mindful of the food you consume and the weight fluctuations that happen daily.
to be continued…
*1 (n.d.). Biology’s response to dieting: the impetus for weight regain. – NCBI – NIH. Retrieved September 4, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/21677272
*2 (2012, April 24). Metabolic Slowing with Massive Weight Loss despite Preservation of …. Retrieved September 4, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3387402/
*3 (n.d.). Biology’s response to dieting: the impetus for weight regain. – NCBI – NIH. Retrieved September 4, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/21677272
*4 (2015, January 22). The role for adipose tissue in weight regain after weight loss. Retrieved September 5, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4371661/
*5 (2017, January 27). Adipocyte hypertrophy-hyperplasia balance contributes to weight loss …. Retrieved September 5, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5477697/
*6 (2016, May 2). Persistent metabolic adaptation 6 years after The Biggest Loser …. Retrieved September 5, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4989512/
