The fuzzy math of weight loss makes me so angry. Once, many years ago, when I was 19 and struggling with body image and eating issues during a deep depression, I sought help from a psychiatrist who wanted to start me on an antidepressant. When I asked if this medication would make me gain weight, he replied, "Well, calories in minus calories out equals weight gain or weight loss, right?" This was the single most useless thing he could have said. I was infuriated, and never saw him again.
He was wrong for so many reasons. Let's address the math first. This basic formula makes some sense, but when applied to real life, real eating, and real bodies it is hardly a balanced equation, for many reasons.
- "calories out" is determined by how your body burns its energy stores, and this is not a fixed constant. Your metabolic rate, or how you burn calories, is changeable and responds to many factors in your body and in your life! Metabolism is not only affected by your level of activity and exercise, but by myriad changing hormonal guidance sytems. Stress, illness, medications, and changes in your sleep cycle have all been proven to significantly change your metabolic rates and tendency to gain or lose weight. Your level of cardiovascular fitness affects how many calories you have to burn in order to complete any given movement or exercise. The same person performing the exact same 1 mile run at the same speed on the same treadmill will burn a varying number of calories depending on how well rested and hydrated you are, how much you've recently been exercising, and the partial pressure of oxygen in the ambient air (i.e., are you running in Denver or Boston), just to name a few factors.
- "calories in" is not quite an exact science, either. Reading the packaging on food and measuring your portions is a good habit if you're trying to control your weight. It's an important way to estimate the number of calories you are consuming, but it is an ESTIMATION. Probably every meal I enter into my LoseIt account is at least 10% discrepant from how many calories' worth of fuel my body extracts from that food. Even if I am meticulous about measuring, weighing, and researching the nutritional info of everything I put in my mouth, it's still only a best guess.
- calories are important, but they're not the only thing.
For example, "water weight" is a real thing. Most healthy humans with normal organ function do not see huge swings in their weight because of hydration status. If you have heart, liver, or kidney failure of any kind, however, your body sometimes struggles to maintain balance and you can swell up with edema or ascites and I've seen patients' weights fluctuate as much as 40kg just from fluid! I am perfectly healthy, and even my medium-sized self sees the scale drop 5 pounds from one day to the next if I'm particularly dehydrated. These are often very short term swings, which is why in medicine (with our heart failure patients) and also in weight loss, we'll often refer to someone "dry weight" as a sort of "true" measure of their body habitus, reflective of their eating and metabolism, not their fluid status.
And don't forget - calories themselves are a measurement. They are not actual items in your body, nor sources for fuel. Your body has ways to use sugars and fatty acids to produce energy, and all these processes involve many molecular conversions from one form of energy to another. A calorie is just a metric of energy use.
Your weight when you step on the scale at any given moment is product of all these interacting moving parts - the calories in the food you've consumed, the way your body has digested and absorbed that food, the calories you've burned, the hormones that regulate everything, and the constant shifts of fluids and electrolytes in your body. The number on the scale is the product of a thousand complex equations, and is not just "calories in - calories out = weight change." You can't directly measure metabolism as it happens in your body, and you can't precisely model the whole equation. Each process in this whole complex system is natural, meaning it is more mercurial than mathematical, more alchemy than chemistry.
So, knowing all that, why I do I get so damn upset when I step on the scale and find it's not the exact number I wanted to see? How can those glowing digits between my toes hold such sway over my sense of accomplishment versus defeat? I know full well that the scale will change tomorrow, or maybe the next day. I know that treating my body kindly and living healthily is far, far more important than the readout on a cheap instrument on the floor of my bathroom. But that moment of stepping on the scale in the morning feels like such a summation of my previous' days efforts, a judgement of my progress. I continue to work hard to divorce my feelings about my health and fitness and progress as a human from the number I see.
My weight is the product of so many more factors than my FitBit can report, although logging food and tracking exercise are valuable tools for weight control. My body is so much more than a weight loss machine. And I am so much more than my weight, my appearance, or my food log. I know these things. And I will continue to remind myself of all of this until I stop feeling discouraged every time the number mysteriously goes up even though I was so good the day before.
This is life, not a numbers game. Keep the ounces in perspective, and don't let anyone reduce your personal journey to an oversimplified, inaccurate equation.