I must admit, for the longest time, I was very confused and unable to understand why calorie restriction and exercise – the eat less/move more approach to weight loss – doesn’t work.
As a chronic dieter, I followed the eat less/move more approach to weight loss for years. I was a dedicated exercise enthusiast and I even got myself certified as a Nutrition coach. And yet, permanent weight loss was elusive. And like most chronic dieters, I believed it was my fault. Any weight I lost, always came back. I was unable to discipline myself sufficiently to successfully calorie restrict and I was unable to discipline myself to exercise without one on one assistance. In fact, I still cannot. Clearly, I had a deeply flawed character.
But once I understood why calorie restriction does not work and I changed the way I eat to match my physiology – weight loss was remarkably easy. I lost the weight I regained after I stopped personal training, and had resigned to my fat fate. I plummeted through the weight loss plateau 5 years of consistent personal training and attempts at calorie restriction could not budge.
I was not deeply flawed. My body was responding beautifully to increased exercise combined with calorie restriction. Exercise increases your appetite and calorie restriction slows your metabolism. Double whammy – you feel hungry and you burn fewer calories (despite increased exercise.)
It’s just so unfair right?
It’s all about physiology and something called homeostasis.
Homeostasis is the body’s ability to adapt to changes in the environment. If the environment is hot, you sweat; if it’s cold, you shiver. Your body will keep your internal temperature around 37oC. Bright sunshine or a dimly lit room – your eyes adjust. In the same way, your body responds to your caloric intake. If you eat fewer calories, your body will burn fewer calories.
In physiological terms, that means your basal metabolic rate (BMR) decreases. Your BMR is the sum total of the energy required to keep your body alive. It includes things like breathing, maintaining body temperature, keeping your heart pumping, maintaining healthy kidney function, liver function and brain function. And you have absolutely no control over this. You cannot will your body to keep its metabolism up any more than you can will your kidneys to stop making pee.
What you can control is your daily total energy expenditure (TEE). Your daily total energy expenditure includes your BMR, plus the thermogenic effect of feeding (TEF – the energy needed to digest and absorb what you eat), plus non-exercise activity thermogenesis (NEAT – the energy expended with fidgeting, sitting up in your chair, typing, walking to the kitchen etc – any non-exercise related activity) plus exercise.
TEE = BMR + TEF + NEAT + exercise
This is where the advocates of exercise for weight loss chime in. It’s true, if you exercise, you will more burn calories than if you sit quietly. When you sit quietly, you burn 1 calorie per 2.2 pounds body weight per hour. If you weight 220 pounds, you will burn 100 calories, sitting quietly. Moderate walking at 2 miles per hour for 60 minutes, burns approximately 133 calories.
Hmm. Not much of difference is it?
Exercise accounts for at most 5% of our total daily energy expenditure. Ninety-five percent of the energy our body burns has nothing to do with exercise. Advocates of exercise for weight loss will also quite correctly argue, being fit will increase your basal metabolic rate. Muscle tissue is much more metabolically active than fat tissue. The more muscle mass you have, the more energy you burn. But we lose up to 5% of our muscle mass per decade after age 30y. We must exercise just to maintain our muscle mass. I’m just not sure how much that is going to change our basal metabolic rate and subsequently our total energy expenditure. My guess is not a lot given that there is not a huge difference between sitting quietly and walking.
Contrary to popular belief, our appetite is not under voluntary control. Our appetite is very tightly regulated by hormones including ghrelin (greh-linn), cholecystokinin (CCK; Ko-le-cist-o-kye-nin), peptide YY, insulin and leptin (leh-p-tin). Ghrelin tells us when we are hungry and should find something to eat, cholecystokinin and peptide YY, tell us when we are full and should stop eating. Insulin is our fat storage hormone and is secreted by the pancreas in response to eating. Leptin is our satiety hormone and is secreted by our fat cells. Leptin tells our brain our fat cells are full and insulin can stop storing excess energy as fat.
This is normal appetite homeostasis – Ghrelin increases hunger, CCK and peptide YY, shut it off. Insulin stores fat, leptin tells it to stop. Perfect.
So what is going wrong?
Calorie restriction messes with all of these hormones. Calorie restriction significantly increases ghrelin – we feel hungry. Multiple, low fat, calorie restricted small meals daily ensures our insulin levels are always high – we are constantly in fat storage mode. And most frustratingly, high insulin levels stop leptin from telling the brain to shut off fat storage.
Calorie restriction makes us feel hungry, promotes fat storage and interferes with satiety. No wonder weight loss is a problem when we calorie restrict.
So in response to calorie restriction our body 1) decreases our metabolism, and 2) messes with the hormones that regulate our appetite. Neither of which are under our voluntary control.
Calorie restriction creates a vicious cycle. We eat less and lose some weight. Our metabolism slows and our hunger increases. We start to regain weight. Determined, we double down eat even less (or at least try) and increase our exercise. We get hungrier and our metabolism slows even more. Our weight starts to increase again. This nasty cycle continues until we are miserable. We are hungry, and because our metabolism is slow we are cold and lethargic and most likely irritable. We give up, return to our old way of eating and we regain all of our weight plus some.
This was exactly my story. I joined a popular weight loss program, lost about 30 pounds, and slowly I started to regain the weight. So, I joined the gym, lost my weight regain, plus a little more. Slowly I rebounded. Doubled down – more exercise. Lost a bit. Gained a bit. Lost a bit. Gained a bit. Over and over for 5 years. More hunger. More cheating. More self-reprimand. Until one day – I simply burst into tears during a training session (sincere apologies to my trainer at the time.) Shortly thereafter, I was done. No more training. No more calorie restriction. I was ready to resign to my fat fate.
And I did. No more exercise, no more calorie restriction and guess what? The weight returned – almost all of it. Then I learned why it was not my fault. And that, made all the difference. And it can make all the difference for you too.
Weight gain (and weight loss for that matter) has nothing to do with willpower or lack of moral fortitude – you are not deeply flawed because you struggle to lose weight. It truly is, not your fault. It’s your physiology working against you.
Have a wonderful week,
Dr Karen
