Fit Versus Thin: Why Thin Isn’t Always Healthier

Leaf through the pages of most fashion magazines and you‘ll immediately notice how thin the models are. Far from looking like the picture of health, these models appear almost emaciated. It’s true that some people, especially young people have higher resting metabolic rates and, potentially, more brown fat that makes it harder for them to gain weight. On the other hand, there are other women and girls who struggle to achieve what they believe is a fashion ideal – being thin. With research showing that obesity is a risk factor for health, some people assume that being at the other extreme, skinny, is healthy. Not necessarily so. Here’s why.

Thin Can Be Unhealthy Too

There’s a difference between being thin naturally and forcing yourself to achieve a low body weight by under-eating. When you restrict calories you deprive yourself of essential nutrients that are vital for good health. Girls and women who reduce their calorie intake too low and over-exercise can lower their estrogen levels to the point where they lose bone mass.

Even naturally thin women are at higher risk for bone loss and osteoporosis. Low bone density leads to a higher risk for fractures including fractures of the hip that carry a high mortality rate. Having a low body weight is also linked with fertility problems, particularly among women who restrict calories excessively to achieve low body weight.

Fit versus Thin: The Epidemic of Fat-Skinny

A percentage of people who are below their ideal body weight fall into the category of “skinny-fat,” meaning they have a high percentage of body fat relative to muscle. Interestingly, people who fall into this category are at risk for obesity-related health problems such as metabolic syndrome, heart disease, high blood pressure, and type 2-diabetes even though they aren’t overweight or obese. This is because they carry a higher portion of visceral fat, the most dangerous kind when it comes to health and disease risk. Body weight isn’t always a good indicator of how healthy you are – body fat percentage and waist circumference are better measures.

According to a study published in the Journal of the American Medical Association, as many as one in four people who fall into the underweight and even the normal weight category are metabolically unhealthy, meaning they have metabolic risk factors that increase their risk for heart disease and other health problems. In contrast, not all people who are overweight or obese have metabolic issues. According to this study, about half of overweight people are healthy from a metabolic standpoint and about one-third of obese people are too. In fact, some people who are “naturally thin” have a variation in a gene called IRS1 that places them at higher risk for heart disease and type 2 diabetes.

As you might expect, regular cardiovascular and resistance training and clean eating is the best way to correct the problem of “skinny-fat” and improve metabolic health. Exercise increases insulin sensitivity and boosts metabolic health while resistance training enhances lean body mass.

Do Overweight People Have a Longevity Advantage?

A recent study published in the Journal of the American Medical Association raises new questions about whether “thin” is healthy. This large meta-analysis that studied 3 million adults showed that being overweight was linked with a lower risk of dying from all causes. This research used BMI to measure obesity, not an ideal measure since some athletes that have a higher percentage of lean body mass fall into the overweight category. Still, it does raise questions about body weight and health. This certainly shouldn’t be a license to overindulge since people who had a BMI over 35 had a higher risk of mortality in this study. It looks like either extreme isn’t ideal. Plus, maintaining lean body mass and as well as some energy reserves in the form of fat becomes more important with age.

What Does This Mean?

Body weight doesn’t necessarily define health. Some people who are underweight based on the scale have a high body fat percentage that puts them at risk for metabolic problems. In addition, being significantly underweight increases the risk of bone loss even in naturally thin women.

The take-home message? Stop obsessing about a number on the scale, focus on resistance training and moderate amounts of cardiovascular exercise to improve metabolic health, increase lean body mass and keep your bones healthy. Being strong and healthy feels better than being weak and skinny – and it may prolong your life too. When it comes to fit versus thin fit wins every time.

References:

Science Daily. “Just Being Naturally Thin May Raise Risk Of Osteoporosis In Women”

JAMA Intern Med. 2013;173(6):470-472.

Nature Genetics 41, 1110 – 1115 (2009)

Medical News Today. “Gene That Keeps You Thin May Raise Risk of Heart Disease And Diabetes”

The JAMA Network. “Higher Levels of Obesity Associated With Increased Risk of Death; Being Overweight Associated With Lower Risk of Death”

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