An overweight BMI is any score from 25.0 to 29.9. BMI, or body mass index, is a number calculated from your height and weight that places you into a weight category. A score below 18.5 is considered underweight, 18.5 to 24.9 is normal weight, 25.0 to 29.9 is overweight, and 30.0 or above is obese.
How BMI Is Calculated
BMI uses a simple formula: your weight divided by your height squared. If you’re working in pounds and inches, you divide your weight by your height in inches squared, then multiply by 703. In metric units, you divide your weight in kilograms by your height in meters squared. A 5’9″ person weighing 170 pounds, for example, lands at a BMI of about 25.1, just crossing into the overweight range.
You don’t need to do this math yourself. The CDC and most health organizations offer free online calculators where you plug in your height and weight and get your category instantly.
What an Overweight BMI Means for Your Health
Falling in the 25 to 29.9 range doesn’t automatically mean you’re unhealthy, but it does signal elevated risk for several conditions. People in the overweight category are more likely to develop high blood pressure, partly because a larger body requires the heart to pump harder to supply blood to all its cells. That extra cardiovascular strain also raises the risk of heart disease and stroke.
The connection to type 2 diabetes is especially strong. Nearly 9 in 10 people with type 2 diabetes carry excess weight. The encouraging flip side: losing just 5% to 7% of your starting body weight can significantly lower your diabetes risk if you’re in a higher-risk group.
Other conditions linked to carrying extra weight include fatty liver disease, sleep apnea (excess fat around the neck can narrow your airway), and certain cancers. In men, colon, rectal, and prostate cancers are more common at higher weights. In women, the risk increases for breast, uterine, and gallbladder cancers. Adults who gain less weight as they age tend to have lower rates of many cancer types overall.
A large pooled analysis of 1.46 million adults found that healthy women who had never smoked and were in the overweight range were 13% more likely to die during the study’s follow-up period compared to women with a BMI between 22.5 and 24.9. For every five-unit increase in BMI across all participants, the risk of death rose by 31%.
Why BMI Doesn’t Tell the Whole Story
BMI is a screening tool, not a diagnosis. It cannot distinguish between fat, muscle, and bone mass. A muscular athlete and a sedentary person of the same height and weight will have identical BMIs despite very different body compositions and health profiles. The American Medical Association formally recognized these limitations, advising that BMI should not be used as a sole measure of health and noting concerns about how it has historically been applied.
Where your body stores fat matters as much as how much you carry. Research from the Mayo Clinic found that people with large waist circumferences were more likely to die younger from heart disease, respiratory problems, and cancer, and this held true even among people whose BMI fell in the normal range. Belly fat in particular has a metabolic profile closely tied to diabetes and heart disease. Measuring your waist circumference alongside BMI gives a more accurate picture of your risk.
Different Thresholds for Different Populations
The standard overweight cutoff of 25 was developed primarily from data on white European populations. It doesn’t fit everyone equally. The World Health Organization has proposed lowering the overweight threshold to 23 for people of Asian descent. This reflects the fact that Asian populations tend to develop higher rates of diabetes, high blood pressure, and high cholesterol at lower BMI levels compared to white populations of similar age and sex. Part of the reason is body composition: Asian individuals are more likely to accumulate fat around the abdomen, which carries greater cardiovascular risk even when overall weight appears moderate.
BMI Categories Work Differently for Children
For children and teens, BMI isn’t measured against fixed cutoffs the way it is for adults. Instead, a child’s BMI is compared to other children of the same age and sex using growth charts. A child is considered overweight if their BMI falls at or above the 85th percentile but below the 95th percentile. At or above the 95th percentile is classified as obese. This percentile-based approach accounts for the fact that body composition changes naturally as children grow.
Small Weight Changes Can Make a Difference
If your BMI places you in the overweight category, the health benefits of losing weight don’t require dramatic changes. Losing 3% to 5% of your body weight can reduce fat buildup in the liver. A 5% to 7% loss can meaningfully lower your risk of developing type 2 diabetes. For someone who weighs 190 pounds, that’s roughly 10 to 13 pounds. Adults who simply gain less weight over time, even without losing existing weight, also see lower risks for several types of cancer including colon, kidney, and breast cancers.