Thin People Shouldn’t Give Weight Loss Advice

Thin People Shouldn’t Give Weight Loss Advice

Or, illusory correlation in action!

By Steve Anthony

An illusory correlation is a perception that there is a meaningful relationship between variables when no such relationship exists. Example: Thin Person: Just eat in moderation and you won’t be overweight — that’s what I do, and see, I’m thin! Or, Thin Person: You just need to be more active; I go to the gym 5 days a week and see, I’m thin.

While clearly, getting regular exercise and eating in moderation is generally good advice, the links between that advice and weight loss are essentially nonexistent.

So why do thin people think they know the secret to weight management?

For one thing, their advice often fits with how we’ve been taught weight management works. We’ve likely all heard someone tell us it’s all about “calories in vs. calories out.” This model says that if you take in more calories than you expend, you will gain weight; if you take in fewer calories than you expend, you will lose weight. This is the nutritional equivalent of saying Jeff Bezos is a billionaire because he saves more money than he spends. While technically true, it glosses over some pretty important details between the spending and saving.

Calories in/calories out is just not a particularly relevant aspect of weight management. In fact, there are conditions under which one can gain weight while eating at a calorie deficit and conditions under which one can lose weight while eating at a calorie surplus.

For another thing, most people don’t understand how the human body regulates weight. It’s a complex process to be sure. In the absence of a true understanding of how weight is regulated in our bodies, we assume that how we behave leads to the results we have. So the thin person who goes to the gym five days a week sees that as the reason they are thin; the thin person who eats in moderation (whatever that means) sees that as the reason they are thin. And the thin person who eats half a banana at breakfast and the other half before dinner thinks that’s the secret. And this is where illusory correlationcomes in: a perception that there is a meaningful relationship between variables when no such relationship exists.

The corollary advice given based on the calories in/calories out model is “eat less/move more.” But as Maria Cross wrote here ( this advice only works in the short-term. And as Dr. Jason Fung puts it in one of his lectures on YouTube, the eat less/move more approach, as a long-term weight loss strategy, “has a perfect record, unblemished by success.”

Those of us who have had trouble managing their weight throughout their lives know that the eat less/move more advice people give us doesn’t work — or at least doesn’t work for us. But, again, without an understanding of how the human body regulates weight, it’s hard to argue the point when you are the overweight one in the argument.

So, what approach does work for attaining long-term weight loss and weight management overall?

In my opinion, it seems it will be important to use an approach that is in sync with how the human body regulates weight. Once we understand how the body processes and reacts to what we eat, we will be better able to evaluate any weight management approach we might see.

A successful, long-term approach should also be healthy. That is, the diet (in the broad sense of the word) should not lead to any nutrient-related deficiencies.

There are several symptoms of protein deficiencies we should be mindful of, such as red or flaky skin, hair loss, brittle nails, loss of muscle mass, and even increased appetite.

Signs of essential fat deficiencies include tight skin, an inability to heal small cuts or scrapes, vision problems and mood issues, including depression.

Signs of carbohydrate deficiencies are — oh, wait, there are no carbohydrate deficiencies. In fact, carbohydrate is a non-essential nutrient.

There are essential amino acids that we get from protein and essential fatty acids we get from fat. These are things our bodies need and that we need to eat to supply our body with them (there a 9 essential amino acids and 2 essential fatty acids). We need other amino and fatty acids, but the body can synthesize these from the 11 essential ones we need to eat. But if we don’t eat the essential 11, we get sick, as described above.

But there are no essential carbohydrates. None. Zero.

If eaten, carbohydrate gets broken down into glucose. And even though we need some glucose, the liver can create all we need through the process called gluconeogenesis. The raw material the liver converts into glucose is body fat. So the human body, if starved of carbohydrate, will take body fat and convert it into the glucose it needs to survive. It’s almost as if we evolved to survive without eating what was, historically, a not-so-prevalent nutrient.

This leads to an interesting question: Given carbohydrate is a non-essential nutrient, why does the USDA, and the fields of medicine and nutrition endorse a daily diet that is 50–65% carbohydrate? And why do they refer to it as a “balanced” diet when half or more of it is a non-essential nutrient? The answer to these questions is hard to believe — maybe I’ll cover that in a separate article.

The point I want to make here is that we evolved in a way that makes eating carbohydrate unnecessary. Yet most of us eat a carbohydrate-rich diet. Is it possible that such a diet works against how at least how some of our bodies metabolize the food we eat? Could that be a cause of the obesity epidemic we have in the US and that is spreading around the world?

Is it possible that carbohydrate tolerance is a spectrum where some people can eat a lot of carbs and not gain weight while others gain weight on a carb-rich diet? Is it possible that thin people (or at least some thin people) don’t need to eat in moderation or go to the gym like they think they do?

So many questions…

References used in writing this article:

Benton, D and Young, H (2017) “Reducing Calorie Intake May Not Help You Lose Body Weight, Perspectives on Psychological Science” Sep; 12(5): 703–714.

Ebbeling, CB et al. (2012) “Effects of dietary composition on energy expenditure during weight-loss maintenance” Journal of the American Medical Association, Jun 27;307(24):2627–34.

Ebbeling, CB et al. (2018) “Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial” British Medical Journal, 363.