Key takeaways:
A lower body weight does not automatically equal good health. People with a low body weight can be at an increased risk of all-cause mortality, as well as certain health conditions.
Weight and body size are very imperfect measures of health. A person’s body composition — including their amount of muscle mass — is a better predictor of health risks than weight alone.
Body size is determined more by genetics than lifestyle choices. So many people in larger bodies are healthy.
Many people assume that having a smaller body or lower body weight is a sign of good health. But this is a common misconception.
A person’s weight is just one of many factors that influences their health. And, what’s more, a low body weight can come with real health risks. Below, we’ll look at why a smaller body is not necessarily healthier, and why a larger body does not mean someone is unhealthy.
What determines a person’s weight?
There are many factors that can influence your weight, and many of them are out of your control. Most of these factors have nothing to do with lifestyle choices, including:
Your genetics
Your unique metabolism (how your body naturally processes and stores energy)
Your age
Your race
Your environment, including where you live and the health resources in your community
Your sex at birth
Your cultural practices
How much sleep you get each night
What types of health conditions you have
Whether or not you take certain medications
How much stress you deal with on a regular basis
Your eating habits
How active you are
These factors can help explain why two people with very similar eating or exercise habits can be at very different weights.
Why do people think being skinny is the only way to be healthy?
In general, Western culture has shed a negative light on people who have larger body sizes. Part of this is the idea that you have to be thin to be healthy, which has largely come from the media. The media is full of celebrities who are thin, and frequently sends the message that you have to be thin to be both beautiful and healthy.
In addition, research has shown that having extra body weight or obesity can increase your risk of developing many health conditions, such as Type 2 diabetes, cardiovascular disease, and more. As an unintended result, this information has led to the belief that people with smaller bodies are healthier than people with larger bodies.
Why skinny is not always equal to healthy
While it is true that having extra body weight raises your risk of certain health conditions, that does not mean that less body weight equals good health.
In reality, weight is just one risk factor for conditions like cardiovascular disease. Other risk factors, such as high blood pressure, abnormal blood sugar levels, and high cholesterol, can affect people at any weight.
Also, since there are many factors that determine weight, some people can have very unhealthy diets and lifestyles and still be at a weight that is perceived as healthy.
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The risk of low body weight
A low body weight can actually be harmful to your health. People who are labeled as underweight — defined as having a body mass index (BMI) of less than 18.5 — are at risk of serious health conditions. These include:
Fragile bones
Fertility problems in females
A weakened immune system, which could lead to getting sick more often
Malnutrition from nutritional deficiencies
Anemia
Higher risk for cardiovascular disease
A large population based study also found that low-weight individuals had a higher risk of all-cause mortality — death from any cause — than individuals with what is labeled a “healthy” BMI. And this was just in the general population. These results do not speak to the serious health and mortality risks associated with eating disorders.
Anorexia nervosa is an eating disorder that can (but does not necessarily) lead to a low body weight. And it has the highest risk of death of any other mental health disorder.
Does the science show that being skinny is healthy?
Research has confirmed that a person’s body composition may be a more accurate predictor of health than their body weight alone. People with high body fat percentages and low muscle mass have a higher risk of developing certain health conditions, even if they have a “healthy” BMI.
In fact, recent research reported that having low muscle mass is linked to:
Reduced physical function
Poorer quality of life
Higher chance of complications during and after surgery
Shorter life span
And this research showed that low muscle mass can occur at any body weight.
Another study suggested that having a high fat mass and a low lean body mass were associated with a higher risk of death. (This was true regardless of a person’s weight or BMI.) But, interestingly, as people got older this relationship began to flip.
The study found that, in older adults, low fat mass was actually associated with an increased risk of death. So the relationship between body composition and health is a complex one, which is why it continues to be studied.
What do the experts say?
In light of the findings in this area, researchers are beginning to push for determining better measures of a person’s health. A recent article, for example, supported the concept of “metabolically healthy obesity.” This term applies to people who have a BMI greater than 30 but have no metabolic health risks, including high cholesterol, blood sugar, or blood pressure.
This further reinforces that having a larger body size does not automatically mean someone is in poor health, just as having a smaller body size doesn’t automatically mean someone is in good health.
The bottom line
Researchers are learning more about the ways that body size impacts health, and the relationship is not as clear as you may be led to believe. The science has shown that a smaller body size does not necessarily mean someone is in good health or at a lower risk for conditions that have been associated with larger bodies. A person’s body composition — which includes body fat, muscle mass, and abdominal fat — is a better predictor of health risks compared to weight alone.
References
American Heart Association. (2020). Common misconceptions about cholesterol.
Blüher, M. (2020). Metabolically healthy obesity. Endocrine Reviews.
Chuang, H., et al. (2012). Correlation between body composition and risk factors for cardiovascular disease and metabolic syndrome. Biofactors.
Diabetes.co.uk. (2022). Skinny type 2 diabetes.
Edakubo, S., et al. (2020). Mortality and risk assessment for anorexia nervosa in acute-care hospitals: A nationwide administrative database analysis. BMC Psychiatry.
Fruh, S. M. (2017). Obesity: Risk factors, complications, and strategies for sustainable long-term weight management. Journal of the American Association of Nurse Practitioners.
Lee, D. H., et al. (2018). Body composition and mortality in the general population: A review of epidemiologic studies. Experimental Biology and Medicine.
Prado, C. M., et al. (2018). Implications of low muscle mass across the continuum of care: A narrative review. Annals of Medicine.
National Health Service. (2020). Underweight adults.
National Institute of Diabetes and Digestive and Kidney Diseases. (2018). Factors affecting weight & health.
Ridley, B. J., et al. (2022). The degree to which the cultural ideal is internalized predicts judgements of male and female physical attractiveness. Frontiers in Psychology.
Roh, L., et al. (2014). Mortality risk associated with underweight: A census-linked cohort of 31,578 individuals with up to 32 years of follow-up. BMC Public Health.
Yang, W., et al. (2007). Genetic epidemiology of obesity. Epidemiologic Reviews.
Zhang, L., et al. (2018). To be thin but not healthy- The body-image dilemma may affect health among female university students in China. PLOS ONE.
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