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Fitness vs. Fatness: Is it better to be skinny vs fit?

Is it better to be skinny vs fit? If you’re a couch potato but thin is that okay? Or is being in good shape, even if you have a few extra pounds better for you?

For more than two decades, debate has raged over whether it’s better to be skinny or fit. It was a 1995 study that started it off with its finding that fitness was associated with better health outcomes, regardless of body size. Since then, studies have continued to compare fitness versus fatness.

It’s long been believed that being overweight, or having obesity, means you’re not in good shape. However, this isn’t entirely true. While fitness levels tend to be lower in people with a higher BMI, the two are not mutually exclusive. In fact, one study found over 50% of women with a BMI 31-33 kg/m2 had a high fitness level.

The Evolving View of Obesity

Of course, the ideal situation is to be in great shape and be thin. These people have the lowest risk for disease and having an early death. But over 1 in 4 Canadians and 2 in 5 Americans have obesity. At the same time, more than 80% of adults are physically inactive. Therefore, few people fall into the category of being in great shape and thin.

While obesity is defined as a body mass index (BMI) ≥30 kg/m2 (overweight ≥25 kg/m2), how we view obesity has changed in recent years. Many medical organizations now consider obesity as a chronic disease. And in 2020, the Canadian guidelines defined obesity not by BMI but as a disease of excess body fat which impairs physical and/or mental health.

Given the challenges with weight loss, there is great interest in how people who are overweight or obese can improve their health. Increasing one’s activity and fitness may play a crucial part.

The Battle: Skinny vs Fit

Some studies have suggested it’s better to be thin rather than active. In one such study, women who were thin yet inactive had a lower chance for early death than those who had obesity and were active. However, in patients with heart disease, being physically active, was more beneficial than having a low BMI. Physical activity reduced the chances of early death even more than weight loss. In both studies, being active was always better than being inactive at the same BMI level.

But those studies looked at physical activity and not fitness. And while the two are related, they’re not exactly the same thing. Fitness is less commonly measured in research because it’s time consuming and requires specialized equipment. However, fitness is one of the strongest predictors of long-term health.

When taking fitness into account, the story seems to be quite different. As expected, in men who were unfit, increasing BMI or waist circumference was associated with a greater chance of early death. However, in those men who were fit, it didn’t seem to matter what size the person was. Effectively, being fit reduced the negative effect of being overweight or obese. Similarly, in adults with diabetes, having a high fitness level reduced the health risk of a high BMI.

And this finding also applies to more than just early death. While overweight and obesity are associated with depression, being fit may be more important. Those people who were fit but obese had a lower chance of being depressed than people who were unfit and lean.

What about those people who have an ideal BMI but aren’t active or physically fit? A review concluded that people who are obese but with a high fitness may actually be healthier than people who are lean and unfit.

skinny vs fit

Do you need to be skinny to be healthy?

So how is it that obesity is associated with increased chances of disease and early death, yet being in good shape can remove this risk? Is there such a thing as being healthy obese? When it comes to risk for conditions such as diabetes and heart disease, it may be the case.

As a result, scientists have created the term metabolically healthy obese (MHO). These people may be obese but do not have risk factors for heart disease such as high cholesterol, high blood sugar and high blood pressure. It’s likely that being active and in good shape has reduced, or eliminated, these risk factors.

While people who are MHO may have a lower risk for disease than people with obesity and risk factors, being MHO is not without concern. Compared to people at ideal body size with no risk factors, MHO people still had a 50% greater risk for heart disease.

On the other hand, being lean by itself doesn’t ensure one is healthy. A person can be lean and still be at high risk for disease. These people are referred to by terms such as thin on the outside but fat on the inside (TOFI) and metabolically obese but normal weight (MONW). They also tend to have a number of risk factors for diabetes and heart disease, and are in poor shape. This may be due to having more fat around their waist. Together, this puts them at greater risk for heart disease and early death.

being fit is good at any body size

The Bottom Line

Both obesity and being out of shape increases your chances for a number of diseases and early death. However, the person who is lean but doesn’t exercise regularly may not be in such good health after all.

Being active and fit is good for you regardless of your body size. And given the challenge of weight loss, focusing on regular activity is a sure way to improve your health make you feel good.

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This post was originally published on March 22, 2018 and updated on February 3, 2021.

15 responses to “Fitness vs. Fatness: Is it better to be skinny vs fit?”

  1. Marise Mathieu Avatar
    Marise Mathieu

    I read all your articles (except those about medication) and find a lot of usefull information and a good motivation to maintain good health habits. Thanks also for all the comments about how people feel or deny or postpone changing long time ways of eating, exercising (or not!), etc. (Sorry for english errors, I’m a french speaking native!).
    Hope you continue to publish this blog and wish you good health!
    Marise Mathieu

    1. Thank you for your kinds words and it’s great to hear you’ve found my articles helpful. I will definitely be continuing. Thanks Scott

  2. Being fat isn’t fit, skinny people are way healthier, obesity is getting so common now that healthy people seem skinny and fat people seem normal

    1. That isn’t always the case. We can’t judge a person’s health by their body size. There are plenty of people who some would call ‘skinny’ who have high cholesterol, high blood pressure, smoke, poor nutrition are sedentary (or have any combination of those risk factors) and far from healthy. While a person whose only risk factor is excess body fat, is active and has a healthy diet, will likely have a lower risk for heart disease, stroke and cancer.

      This is not to say that either of the two situations are healthy or ideal, just that being skinny should not be confused with being healthy. There is more to health than body size.

      Our research (https://bit.ly/2EXIlpE) has also indicated that certain ethnic groups accumulate inner abdominal fat (visceral adipose tissue), which is associated with increased risk for disease, even at ideal body size.

      As you point out, obesity is increasing and in some populations there are more people who are overweight or obese than not. This would therefore make it seem like being obese is normal. As you allude to, we can’t confuse ‘normal’ or common with what is healthy either.

  3. Skinny people live longer. They have less health problems than those who are obese. Look at Japan and you will notice that people are thin and healthy.

    1. Thanks for the comment.

      Most the times, yes, but not always. Just because someone is thin, doesn’t mean that person is healthy. It’s not easy to tell if a person is healthy just by looking at their size and weight as I discuss in this post: https://drscottlear.com/2018/10/24/your-weight-cannot-tell-you-how-healthy-you-are/

      Also, once people get into their 70s and 80s, excess body fat doesn’t seem to matter, and in some cases is associated with longer life.

  4. My friend and I were just talking about this the other day and I think it is very interesting/ I do think that people can be “fat” but be fit at the same time. I was reading this and it defined it in a way of reframing it, https://www.ez.insure/landing/2022/04/the-fat-but-fit-debate-rages-on/ and I think it is worth a read and I would love to hear your thoughts on it!

    1. Thanks for sharing the link. A very well-written article. Most definitely at any body size and shape, being active can improve a lot of health markers even if weight (or body fat) doesn’t change. With weight loss so hard (and sometimes discouraging), focusing on lifestyle behaviours can be a much better option.

  5. We as a world culture should have a mindset where everyone has at least a certain minimum of aerobic fitness. This would significantly reduce healthcare costs, boost productivity and all this ultimately means is more happiness in the world! Governments should not be involved. People can and want to think for themselves, particularly when the payoff of sustaining aerobic fitness is priceless.

    1. I agree! There is so much joy in being active but our society seems to put up so many barriers, whether environmental or social. And true, having someone or an institution tell people what to do won’t work for most people. They need to realize the fun that exercise and fitness can provide and then they will keep doing it.

  6. Dr. Lear, you are high performance Writer-Dr. about physical activity and Health!! What a splendid article. Congrats from Spain. Regards

    1. Thank you for the kind comments! Glad you enjoyed the article.

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