The idea that the body works on a simple calories in/calories out (ci/co) model is one of the most pervasive myths that I hear. This particular myth is extremely damning to us fats since the idea is that:
If you just eat less, exercise more and create a caloric deficit (ie: do not give your body the amount of fuel it requires to function), you will lose weight and therefore be more healthy. If you fail to lose weight, it just means that you lack the will-power to
The following blog is written to be clear and accessible. If you want something more science based and researched then this is the post for you!
I’ve already talked about the conflation of the concepts of weight and health, so today let’s just talk calories in and out.
It sounds really logical, especially if you don’t understand how the human body actually works.
First, it turns out that accurately calculating the calories out side of the equation is at best an awfully indirect science producing questionable results.
The Basal Metabolic Rate (BMR) formula is one of the most popular used to determine how many calories we burn at rest. But the formula doesn’t account for muscle mass, which utilizes more calories than other body tissue at rest. Except that there is controversy about just how many calories a pound of muscle utilizes – some reputable scientists say that it burns 35, some say 10. Also, most methods used to measure muscle mass are fairly imprecise, or really expensive, so very few people have access to a correct measurement even if we could use that number to get an accurate BMR, which we can’t.
Besides which, a BMR-type calculation would be reasonable if we were a lawnmower. We can calculate the fuel needs of a lawnmower and then have a reasonable expectation of how much grass it can mow and what will happen when the fuel runs out.
Ready for a blinding flash of the obvious? Our bodies are not lawnmowers. The way that we utilize fuel (calories) and what happens when we run out is vastly different and extremely individualized and affected by all kinds of things including:
- Smoking/Alcohol consumption
- Past Caloric Restriction (dieting) history
What concerns me even more is that semi-starvation is advocated based on the idea (really, the desperate hope) that a starved body will burn excess fat for fuel. That’s not necessarily the case. Your body is really good at surviving. It is not so good at fitting into a cultural ideal of beauty. The body doesn’t think of calories as evil things that take it farther from an arbitrary standard of beauty, it thinks of calories as fuel to do its job. When you give your body less calories than it needs to perform its basic function it does not think “look how disciplined you are to underfeed me so that we can become smaller”. It thinks “Holy shit, I’m starving. I have to do something!”
Let’s go back to the lawnmower example:
If I give my lawnmower half of the gas it needs to cut my lawn, it will simply stop working half-way through. If tomorrow I only give it 1/2 of the fuel it needs, only 50% of my lawn will get cut. My lawnmower will never adapt to use less fuel, it just stops working.
If I give my body half the fuel that it needs just to lay in bed all day, and proceed to run on a treadmill it doesn’t stop – it adapts. My body can’t imagine a scenario in which it needs food, there is food, but I’m intentionally starving it, so it interprets this situation as “I’m starving, there is no food, and I have to run away from something”.
If I continue to underfeed my body while making physical demands it will likely drop weight at first while adapting to function on fewer calories, even if that means performing those functions (you know: thinking, breathing, heartbeat, walking etc) non-optimally. If I continue underfeeding for the long-term I will experience negative impacts (see below). If I stop underfeeding my body there is a good chance that my body will maintain it’s adapted lower level, at least for a while, and store the extra fuel as fat. My body is trying to help me out – what it has learned is that I live in an environment where sometimes starvation happens at the same time that massive physical labor is required, so it’s storing up fuel for the next starvation/high physical activity period. If I continue to do this over time (as in the case of yo-yo dieting), then the damage to my metabolic rate and my body’s functions can be severe.
And that doesn’t even touch the psychological toll that underfeeding your body takes on you. In the Minnesota Semi-Starvation Study participants who were restricted to 1/2 of their normal food intake for 12 weeks experienced depression (up to and including serious self-mutilation), hysteria, marked food preoccupation, disordered eating patterns, guilt about eating, decline is physiological processes, concentration, comprehension and judgment, and a 40% drop in BMR. For many the disordered eating continued for 5 months or more after the study was concluded.
So while semi-starvation (also known as dieting) seems like a reasonable weight loss technique if you believe in a ci/co equation, I have to judge it on three standards:
Validity of Methodology
Fail. The fact that I can’t accurately calculate how many calories my body will expend or predict how my body will respond to prolonged starvation makes this methodology invalid.
Probability of Success
Fail. The use of caloric deficit has a success rate of 5% over 5 years – that’s within the margin of error for most studies and is an unacceptable success rate for me.
Acceptability of Risks
Fail. I’m risking my current excellent physical and psychological health for a chance at a smaller body. That, for me, is an unacceptable risk.
Which is why I’m sticking to my plan of engaging in healthy behaviors, giving my body the fuel it needs, and letting it determine what size it’s going to be.