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4 Weight Loss Myths Exposed

unicorn-croppedEditor’s Note: This article was first published in June of 2013. It is being reprinted as part of a new weekend series at PJ Lifestyle collecting and organizing the top 50 best lists. Where will this great piece end up on the list? Reader feedback will be factored in when the PJ Lifestyle Top 50 List Collection is completed in a few months…

The hypothesis: a slow carb diet with intermittent fasting, along with continuing to work for greater integration of exercise into my daily life, will help me lose weight and improve my still-too-high blood sugar. This is the third experiment of a 13 weeks duration, in an ongoing series. Follow my daily updates at Facebook and join me on Fitocracy to follow my progress there, of which there will be some. Honest.

13 Weeks: Season 3, Week 3

I've been personally interested in weight loss and associated things pretty much my entire life. Long-time readers will remember me mentioning being insulted about my weight -- told I was repulsive, in fact -- when I was seven or eight. I first started actively dieting, hoping to lose weight and not be repulsive, when I was about 12, and immediately ran into trouble with it. After a certain length of time, even strictly following a 1200 kcal a day diet, I'd stop losing weight.

Since this was well-known to be impossible, it must have been that I was cheating on the diet. I knew I wasn't, but who's going to believe a 12 year old?

Fast forward to when I was working on my PhD at Duke Medical School. By this time I was considerably more sophisticated -- well, except emotionally, I still felt basically that I was repulsive -- and I had started reading seriously about weight regulation. I discovered that a whole lot of things I'd been told were absolutely certain, weren't. Many of those things are still generally believed, and I think they keep people from doing what is useful, get them to do a lot of things that aren't particularly useful, and frankly cause many people to despair.

Myth #1: The "Ideal" Weight Is Healthiest.

This one has made recent news. Our idea of what is an ideal weight comes originally from studies done by life insurance companies. The insurance company actuaries spend their time trying to decide how much to charge for an insurance policy, which is essentially a bet: you are betting the insurance company that you will die young, and the insurance company bets you will live to a ripe old age. (I've explained the basic math of insurance on PJM before.) So insurance companies, primarily MetLife, did studies in the '50s and computed ideal weights from them.

These studies were very empirical, and they really were aimed entirely at determining how much to charge middle-aged white people for insurance. They did a good job of that, but they didn't account for any number of confounding factors. However, once they had published the tables, these tables went from being essentially descriptive -- "middle aged people seem to live longest in these height/weight ratios" -- to be taken as prescriptive -- "everyone's ideal weight is given by these tables of height/weight ratio." Now we define these "ideal weights" in terms of body-mass index, BMI, which sounds much more precise and scientific, but turns out to be simply a height/weight ratio.

Pretty much anyone can see that BMI is questionable -- for example, a champion bodybuilder with a competition body fat of 3 percent may well have a "very obese" BMI. (On the other hand, it's unclear that very low body fat is necessarily healthy either -- in fact, we know it's certainly not healthy for women.)

The problem is that epidemiology, the study of health and disease across large populations, keeps finding results that don't quite fit this idea of ideal weight. Most recently, a study by Katherine Flegel and others published in January of this year showed that the notion of ideal weight was massively oversimplified. The study found two things: first, that for younger people, BMI doesn't have any strong effects, and as you get older, the BMI associated with the least likelihood of dying increases.

In other words, if you don't want to die the data suggests you actually want a slightly higher BMI as you get older.

What's more, other studies say that BMI isn't as good a predictor as simply the length of your belt -- the larger your waistline, the more likely you were to have a whole lot of different health problems like type-2 diabetes. (This one does fit the bodybuilder example, too -- bodybuilders do generally have small waists.)

Now, this can be taken too far -- there's no doubt that real obesity has bad effects on your health. (My knees would tell you that, if asked. And if knees could talk.) But the truth is that being a little overweight is either not harmful or may actually be helpful.