Does this sound familiar?

You decide it’s time to lose some weight.  There’s a hot new diet you’ve been hearing about and people you know swear it’s working for them.  You buy a book about the hot new diet; maybe you buy a couple of books about the hot new diet to get more meal plans and more recipes.  You might sign up for specially delivered diet meals. You go on the diet and you start losing weight. Awesome, the diet works. Until it doesn’t. Your weight plateaus and you still weigh more than you would like to.  You stick with it. Maybe you start to lose weight again and maybe you don’t.  If you do, your weight soon plateaus again and you’re stuck. What happened?

The weight loss industry would have you believe one of two things caused your diet to fall short of producing the results you desired.  One possibility is that it wasn’t the right diet.  There are plenty of other diets out there and you can buy the books and try those.  And if that doesn’t work, there will be another hot new diet any day now that people will rave about and you can try that one. The other possibility is that you’re a failure.  If you’d stuck to the diet, you’d have lost the weight. But you didn’t.  You failed.  Better luck next time.

Is this what happened? You’re a failure or it was the wrong diet? Probably not. What probably happened was that your body responded to the diet in exactly the way the human body is expected to respond to a sustained decrease in the number of calories consumed every day.

Why didn’t your diet books tell you this was going to happen?

To begin to get an answer to this question, let’s take a look at the diet industry. At the end of 2013, the weight loss industry in the US was a $61 billion a year business. 61 billion is an incomprehensibly large number. Break it down. In order to spend $61 billion a year Americans spend about $1,934.30 per second on diet products and services and they do this every second of every hour 24/7/365. If you make $50k per year, Americans spend a little bit more than your annual income on weight loss products and services every 26 seconds. If you work for 50 years and average $50k income per year, Americans spend more on diet products and services than you will make in your entire life every 22 minutes.

Meanwhile, according to the Centers for Disease Control and Prevention the average adult American male is 5 feet, 9.3 inches tall and weighs 195 lbs and the average adult American female is 5 feet 3.8 inches tall and weighs 166.2 lbs. Somebody is getting fat and it’s not just the people who are throwing money at diets that don’t produce lasting weight loss.

Scientists and physicians who aren’t trying to sell you something and who work in the area of diet and weight control have repeated the same simple message for many years. The most important factor determining weight loss is the difference between the number of calories ingested and the number of calories burned on a daily basis.  There are many factors that affect caloric intake and burn and many of them are not fully understood but the  general conclusion that you will lose weight if you consistently burn more calories than you ingest over the course of a day is very well established. It’s that simple.

This is the reason that your new diet worked. Suppose that before you started dieting your weight was fairly stable. Weight stability happens when the body is in energy balance, which means that, on average, the calories burned every day are roughly equal to the calories ingested every day. You start a new diet and reduce the number of calories you ingest during the day. Now that energy balance has been disrupted; you’re burning more calories than you’re getting every day. Under most circumstances the missing calories are provided by metabolizing stored fat and you lose weight.

Notice that this doesn’t have anything to do with which diet you’re following. Any diet will work because following any diet will usually result in ingesting fewer calories than your body typically burns in a day.  You don’t even have to follow a diet.  All you have to do is cut down the number of calories you ingest every day and do it consistently. In other words, you don’t need to give the weight loss industry any money in order to lose weight. The weight loss industry doesn’t publicize this for obvious reasons.

So, why does your diet stop working after you’ve been following it for awhile? Your daily activity hasn’t changed so you should be burning the same number of calories per day. You’ve stuck to the diet so the number of calories you ingest are still lower than the number you’ve been burning.  Why aren’t you continuing to lose weight?

The human body is a sophisticated homeostatic system which means that it adapts to changing conditions in order to keep important system parameters like temperature within an optimal range. For example, if the core temperature of the body gets too hot, you sweat to rid yourself of excess heat; if core temperature gets too cold, you shiver to generate more heat.

Another example is metabolic homeostasis which refers to the body’s mechanisms for maintaining a balance between caloric intake and caloric burn. Metabolic homeostasis is more complicated than previously thought and much about it is currently not well understood. One thing that appears to be soundly supported by the available evidence, however, is that the body adapts to a regular, sustained reduction in caloric intake by reducing the number of calories needed to fuel the level of daily activity that was typical before the calorie reduction took place.

This is the reason your new diet stopped working. Suppose that on a typical day your regular activities burn 2000 kilocalories and you ingest about 2000 kilocalories in food during the day.  Your caloric intake and burn are balanced and your weight is stable.  Then you go on a diet and ingest only 1800 kilocalories a day.  At first you lose weight because the 1800 kilocalories you ingest is less than the 2000 kilocalories you burn each day.  However, if you stay on this 1800 kilocalorie per day diet for a period of time, your body will adapt to that reduced caloric intake by enabling you to engage in the same activity you were doing every day before you began the diet while only burning 1800 kilocalories.  Once that happens caloric intake and caloric burn are balanced again and you stop losing weight.

Notice that there’s nothing here about finding the right diet or about personal failure. There is no right diet. Any diet that is followed consistently will stop working because the body will adapt to the reduced number of calories that are ingested every day. You didn’t fail. Your body did exactly what was expected in the face of a sustained reduction in caloric intake; it adjusted caloric burn so that energy balance was once again achieved.

From the point of view of the diet industry this is almost the ideal scam. You can sell people any diet because any diet will work that involves reducing the number of calories ingested every day.  People lose weight and more products and services are sold.  If people stick to the diet, metabolic homeostasis will come into play and the diet will stop working. When that happens all the weight loss industry has to do is sell people on the idea that either (a) it was not the right diet for them, or (b) they failed at dieting. In either case they’re set up to try it again with the next round of weight loss products and services.

There are two general approaches you can take if you want to lose weight. First, you can tinker with your caloric intake levels and caloric burn activities until you find an equilibrium point where you are in energy balance, you are happy with your weight, and you are enjoying your life. It will take patience, discipline and a willingness to think for yourself and experiment with different intake levels and burn activities when metabolic homeostasis brings you to a weight plateau.

The other option is that you can contribute your money to the weight loss industry so it can continue to gorge on billions of dollars every year. Following this path will also take patience and discipline. It will also take a willingness to let the diet industry do your thinking for you while you spend more money on new diets and new exercise programs when metabolic homeostasis brings you to a weight plateau.

It’s your life, your time, your money, and your choice.