The key to effective weight loss is to burn more calories than you consume, right? This formula is widely accepted and preached everywhere we turn – on news and reality shows, in magazines and newspapers, even in doctors’ offices. Almost every eating and weight loss plan centers on the calories-in-to-calories-out formula at its basic core. The bottom line? If you burn more calories that you consume, you’ll lose weight. Sounds simple right? I largely disagree.
These eatings plans (i.e. diets) focus on teaching people how to trim calories from their dietary intake and/or increase their activity level. Do the two examples below sound familiar?
- If a small latte contains 200 calories, if you eliminate one latte per day for a year, you should lose 20.8 pounds a year if you change nothing else. (200 calories x 365 days/year divided by 3500 calories/pound = 20.8 pounds lost)
- If you burn an extra 100 calories/day by taking the stairs and parking in the back of the parking lot, you should lose 10.4 pounds/year if you change nothing else. (100 more calories burned/day x 365 days/year divided by 3500 calories/pound = 10.4 lbs. lost)
Has this actually worked for anyone long-term, over the course of several years? Yes, perhaps it has worked for a handful of people, and I’m genuinely happy for them. But in general, people are better off doing nothing than touching a diet. (Tracking calories in and out, points, or portion sizes are forms of dieting.) UCLA researchers conducted a rigorous analysis of 31 long-term weight loss studies and determined that “…dieting is actually a consistent predictor of future weight gain.” Dieting is a predictor of weight gain in the long-term.
Perhaps in its strictest form, the calories-in-to-calories-out formula actually works. If a person is incredibly honest and diligent, she can track every single morsel of food that enters her mouth. However, the other side of the equation makes a very lofty assumption. It assumes you can actually measure how many calories you are burning each day. I contest that calorie burn is incredibly individual and difficult (if possible) to measure accurately. Therefore, the calories-in-to-calories-out formula is not an effective weight-loss tool.
Calorie Burn is Incredibly Individual
Daily calorie expenditure depends on so many factors:
- What is your height and weight?
- How much lean muscle mass are you carrying vs. fat?
- Two people can be the exact same height and weight, but if one of them is carrying more muscle, he or she will burn more calories at rest and at activity. You can’t assume that two people of the same height and weight will burn exactly the same number of calories when they run a mile, sleep, or sit at a desk.
- What is your gender?
- What are your hormone levels?
- Are you a fidgeter or comfortable being still?
- What is your eating and dieting history?
- Someone who has dieted or limited calories throughout their life has taught their metabolism to burn food slowly to preserve life and avoid starvation. Their calorie burn would be quite different from someone of the same height, weight, body composition, and gender who had eaten freely and never dieted.
Our bodies make due with what we give them
I first began to question the calories-in-to-calories-out formula when I was competing in Division 1 cross country and track in college. The daily activity level of my teammates and I was quite intense:
- We ran 40-70 miles/week (which varied by individual and where we were in our training cycle).
- We ran three intense speed workouts a week.
- We lifted weights twice a week.
- We walked several miles every day – to, from, and all around campus with heavy backpacks on our backs.
- We studied for hours each day, burning high levels of glycogen in the brain.
I quickly observed that on paper, our daily calorie consumption no where neared how many calories we should have been burning with our heavy activity level. If we had used standard equations to calculate our daily calorie burn, we would have been constantly running a deficit and constantly losing weight. However, for most of us, our weight remained stable. Our bodies simply made do with what we had.
I’ve heard of competitive runners who struggled with eating disorders and reached a point where if they ate more than a tiny amount of food, something like 1000 calories/day, they would gain weight. That simply should not be possible if we calculated their daily calorie burn based on standard equations and compared it to their caloric intake. Their metabolisms slowed to account for the small amount of food they were eating in order to maintain a stable weight.
Our bodies simply make due when they fear there isn’t enough food coming in. For thousands of years, our ancestors were faced with famine and the threat of starvation. As a survival tactic, their bodies learned how to very efficiently process food, slow down caloric burn, and store calories to avoid starvation. Our ancestors passed this process of adaption to us, and our bodies still work the same way. When there aren’t enough calories coming in over a period of time, our metabolism slows to make due with the food coming in. In the beginning, yes, if you consume fewer calories than you burn, you will probably lose weight for the first few weeks or months; but over time, this often results in a slower-burning metabolism, food cravings and binges, and an obsession with food. Our bodies are amazing, survival machines. They don’t know the difference between dieting and famine.
Even though I try to consistently eat every time I’m hungry, I still feel like my metabolism adjusts to my calorie intake and activity level. Right after I finished college competition, I immediately gained quite a bit of weight even though I continued to work out consistently; however, over the next several months, my body adjusted to my new activity level and my weight returned to a more normal range for me.
For the next several years, I was a recreational runner, logging 30-35 miles/week with only occasional speed workouts. When I chose to train for the Newport marathon in the spring of 2012, my miles increased and I consistently ran two speed workouts a week. As a result, I was starving all the time. One night during the Newport training cycle, I ate a solid dinner of homemade soup, bread, and veggies. Afterward, I ran to the store to pick up a few things. By the time I got there, I was hungry again and picked up a Burgerville cheeseburger. I felt better for a little while, but by the time I was out of the store, I was hungry again and tore into a bag of Doritos. Some days I simply felt like I couldn’t get enough food. Since Newport, I’ve trained for a couple of other marathons. While I still have days when I want to eat everything in sight, I can tell my body doesn’t need as much food as it did when I was training over two years ago. My body has adjusted to a higher activity level. Justly or unjustly, I believe our bodies are very efficient and make due with what they get.
Calorie burn devices are not accurate enough
Yes, there are devices such as the FitBit, Nike FuelBand, and BodyBugg that track activity level and intensity throughout the day. Even these devices are not nearly accurate enough. One Saturday morning I was doing a long marathon training run with a friend. Her Nike FuelBand lit up in the middle of the run saying she had met her total activity goal for the day. We still had miles to run and it was probably only 9am. For the next 12-15 hours, she would be moving and burning more calories.
Even the BodyBugg, which suggests it can estimate calorie expenditure with 92% accuracy (through an accelerometer, measuring heat flux, galvanic skin response, and skin temperature), isn’t accurate enough. For a person burning 2000 calories/day, an 8 percent margin of error means the BodyBugg is off by 160 calories every day (a potential 16.7 lb. swing each year).
Even if you do successfully run a calorie deficit for some time and lose weight, what is the long-term impact? If your body becomes alarmed that you’re not getting enough calories, it responds by slowing metabolism and cravings ensue. Every brownie, cookie, and ice cream sundae begins to look irresistible.
Why do we assume our bodies absorb every calorie we consume?
On the “calories in” side of the equation, why do we assume our bodies absorb every calorie we consume? Have you had a time when you felt like what you’d eaten recently went right through you? Perhaps you’d eaten more than normal at a party, ran too close to a meal, or ate something that disagreed with you. I believe there are times when our body chooses to release a portion of what we’ve eaten for whatever reason. The calories-in-to-calories-out formula is also not reliable because we can’t assume we are actually absorbing every calorie we eat.
The calories-in-to-calories-out formula simply oversimplifies weight loss
Weight loss is a highly complicated, delicate process that relies on so many variables. Simplifying weight loss to this level is insulting. It’s insulting to the women I’ve seen who faithfully exercise and eat well and still can’t sustain long-term weight loss. Why aren’t they losing despite their diligence? Most likely their metabolism has slowed to accommodate to too little food coming in. (Most likely they also experience strong food cravings as a result of depriving themselves too much for too long.) They have effectively taught their bodies to live on less. Only when enough calories and nutrients come in regularly does the metabolism shift into a burning state.
Does this mean I advocate flagrant overeating and eating crap? Of course not. So what’s a person to do who wants to nourish their body with the right amounts and types of food? Who wants to find their own natural, healthy body weight? The best thing I can recommend is to begin listening to your body and eat every time you’re hungry; slow down when you eat and really taste and savor your food; stop eating when you’re satisfied with full permission to eat again when you’re hungry. Focus on eating foods you love that make you feel good. In short, employ the process of intuitive eating. Your body will teach you the right types and amounts of food you need to thrive if you listen. Intuitive eating has made me so happy. I haven’t found anything better.
If you want more information about intuitive eating, check out my earlier post on the topic. I also highly recommend the book Intuitive Eating: A Revolutionary Program that Works by Evelyn Tribole and Elyse Resch.