Is Being Skinny Healthy?
You would think this would be a fairly simple question to answer. It's not. The prevailing notion is that thinner is healthier and higher weights are less healthy.
Researchers have followed millions of people trying to determine which body weights are associated with living the longest. And the results are surprisingly inconsistent.
So What Weight Is Healthiest?
One very large analysis of almost four million carefully selected participants found the lowest death rates at BMIs between 20 and 25. Other major research has found the lowest death rates between BMIs of 25 and 30—the category still officially labeled “overweight.”
A Note About BMI: BMI is an imperfect measure and can't tell us how healthy an individual person is. But because it's the measure used in much of the large-scale research on weight and mortality, it's useful here for understanding how body weight and mortality are associated across large groups of people.
A 2024 systematic review of 82 studies involving more than 2.7 million people again found the lowest death rates among people with BMIs between 25 and 30.
But what does a BMI of 20, 25, or 30 actually mean in pounds? The chart below shows the weight ranges associated with the lowest death rates in these different studies.
One thing before we look at the actual weights: Numbers can easily become comparison points, particularly when you've spent years being taught that lower is better. That's not what these numbers are for. In fact, they may challenge that idea.
| Height | BMI 20–25 | BMI 25–30 |
|---|---|---|
| 5'0" | 102–128 lb | 128–153 lb |
| 5'1" | 106–132 lb | 132–158 lb |
| 5'2" | 109–137 lb | 137–164 lb |
| 5'3" | 113–141 lb | 141–169 lb |
| 5'4" | 117–146 lb | 146–175 lb |
| 5'5" | 121–150 lb | 150–180 lb |
| 5'6" | 124–155 lb | 155–186 lb |
| 5'7" | 128–160 lb | 160–192 lb |
| 5'8" | 132–164 lb | 164–197 lb |
| 5'9" | 136–169 lb | 169–203 lb |
Think about that for a moment.
In these studies, the weight associated with the lowest death rates for someone who is 5'4" could fall anywhere from roughly 117 to 175 pounds.
That's a long way from the idea that health requires being skinny.
It's also a long way from the idea that science has identified some narrowly defined “healthy weight” you're supposed to reach.
Why do studies involving millions of people come up with such different answers? There are some fascinating—and important—reasons. And if research is showing that larger bodies can be healthy, why don't we hear more about that? I dig into these questions in a separate article about why weight research can be so contradictory.
For now, let's stay with your question.
Can You Get Too Skinny to Be Healthy?
This is where the research gets particularly interesting.
Remember that very large analysis mentioned above that found the lowest death rates between BMIs of 20 and 25?
It found something you might find shocking about being skinny and health: below BMI 20, death rates actually increased.
Compared with people at BMI 20–25, mortality was:
about 13% higher at BMI 18.5–20
about 51% higher at BMI 15–18.5
Check out the chart below to see what this actually means in pounds.
| Height |
BMI 15–18.5 (51% higher mortality) |
BMI 18.5–20 (13% higher mortality) |
|---|---|---|
| 5'0" | 77–95 lb | 95–102 lb |
| 5'1" | 79–98 lb | 98–106 lb |
| 5'2" | 82–101 lb | 101–109 lb |
| 5'3" | 85–104 lb | 104–113 lb |
| 5'4" | 87–108 lb | 108–117 lb |
| 5'5" | 90–111 lb | 111–121 lb |
| 5'6" | 93–115 lb | 115–124 lb |
| 5'7" | 95–118 lb | 118–128 lb |
| 5'8" | 98–122 lb | 122–132 lb |
| 5'9" | 101–125 lb | 125–136 lb |
And these results were not simply because thinner people were sicker to begin with.
For this analysis, researchers excluded people who had ever smoked as well as people with certain chronic diseases. They also excluded anyone who died during the first five years of follow-up, further reducing the possibility that an existing illness was responsible for their lower weight.
Another enormous analysis, this one pooling data from 19 prospective studies and nearly 1.5 million adults, found a similar pattern among healthy people who had never smoked.
Among women, mortality was higher at BMI 18.5–19.9 and substantially higher below 18.5.
But the increased risk doesn't suddenly appear at a BMI of 18.5.
Death rates actually begin to increase at around BMI 20!
For a 5'4" woman, that's around 117 pounds.
Those numbers are strikingly similar to the body weights our culture has spent decades telling women they should achieve.
So yes, we have been enculturated to want to be skinny. But at what cost?
The Cultural Ideal and the Health Ideal Aren't Necessarily the Same Thing
Years ago, while studying cultural ideals about women's bodies, I started looking up the published heights and weights of women whose bodies were being held up as particularly desirable.
Again and again, I calculated BMIs around 18 (and lower).
This wasn't a formal scientific study. It was something I did out of curiosity while researching and teaching about our cultural obsession with thinness.
Published research on fashion models has found something remarkably similar: average BMIs around 17–18, with many models falling below a BMI of 18.5.
So consider the contradiction.
At roughly the same end of the weight spectrum that our culture has repeatedly presented to women as aspirational, large mortality studies are finding increased risk of death.
That doesn't mean BMI 18 is automatically unhealthy for every individual.
It does mean we should stop assuming that becoming thinner necessarily means becoming healthier.
The research simply doesn't support that.
Research
Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. Global BMI Mortality Collaboration. The Lancet, 2016.
Impact of Body Mass Index on All-Cause Mortality in Adults: A Systematic Review and Meta-Analysis. Systematic review and meta-analysis of 82 studies involving more than 2.7 million people, 2024.
Body-Mass Index and Mortality among 1.46 Million White Adults. Berrington de Gonzalez A, et al. New England Journal of Medicine, 2010.
Association of All-Cause Mortality With Overweight and Obesity Using Standard Body Mass Index Categories: A Systematic Review and Meta-analysis. Flegal KM, Kit BK, Orpana H, Graubard BI. JAMA, 2013.
Body Mass Index and Risks of More Than 40 Cause-Specific Mortality in Chinese Women: A Prospective Cohort Study. Hu J, et al. Journal of Cachexia, Sarcopenia and Muscle, 2026.
Higher orthorexia tendency among female fashion models: an empirical international study. International study of 179 female fashion models, 2024. Mean BMI among models was 18.1, compared with 22.1 among controls.
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