A BMI of 21 is considered a very healthy BMI for women and men. So does this mean that registering a 21 BMI is enough to guarantee good health?
Not necessarily. While many people who have a BMI of 21 are perfectly healthy, body mass index—especially within the normal range—can’t tell you anything specific about your health because it doesn’t measure adiposity (body fatness) or muscle mass.
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Is a BMI of 21 good for a woman?
Is a BMI of 21 good for a woman? A BMI of 21 is good for women in the sense that a female who registers a 21 BMI score likely doesn’t need to worry about her weight.
The problem is that BMI doesn’t factor in a woman’s body fat or muscle mass, which are two very important physiological attributes that can greatly affect your health.
Although some research does suggest that BMI can measure body fat, it can’t do so directly because body mass index literally just gives you a score based on your height and weight.
As an example, you could theoretically have extremely low levels of muscle mass while having excessively high body fat while registering a “healthy” BMI of 21. Now do you see why a normal BMI doesn’t guarantee good health?
Is a 21 BMI good for a man?
Is a 21 BMI good for a man? A BMI of 21 is a good body mass index for a man because it means that he has a healthy body weight.
That said, some men who register a 21 BMI score have what might be termed a skinny fat physique. In research, this is often referred to as sarcopenic obesity, which is where a person has too much body fat but also too little muscle mass.
For this reason, some males who have a BMI of 21 may need to go through a period of body recomposition whereby they lose body fat and gain muscle mass.
Gaining muscle and losing fat at the same time is easier when you’re out of shape because your muscles have more growth potential when they’re relatively untrained.
What does a person with a 21 BMI look like?
While we can’t say for certain what a person with a 21 BMI looks like (because BMI doesn’t measure body composition), we can go through a few likely physiques.
As mentioned above, you can have a 21 BMI or a 21.5 BMI while being unhealthy if you lack muscle mass and have too much body fat.
Conversely, an individual with a BMI of twenty one can have plenty of muscle mass and a low body fat level, which would likely result in a much healthier body than in the previous scenario.
Naturally, most people will fall somewhere between these two opposing physiques.
Of course, your overall build and bone structure can also influence how heavy you are for your height and, thereby, your BMI score.
For example, two people could be the exact same height, but one of them might have a really broad build and more muscle mass, causing them to have a higher BMI.
BMI 21 variations
When you input your height and weight into an online BMI calculator, you’ll get a precise score such as the ones below.
A 21.1 BMI means that you have a healthy body weight for a person of your height. Whether or not you need to gain muscle or lose fat depends on your body composition.
If you have a BMI of 21.2, then you should be happy that your body weight is well under control; you’re comfortably above and below the underweight and overweight categories.
A BMI of 21.3 is a sign that your body weight is where it should be. Still, some people with a 21.3 BMI may benefit from lowering their body fat level and/or gaining more muscle mass via resistance training.
Those who have a 21.4 BMI likely don’t need to worry about their weight because it’s well within the healthy range for men and women.
If you have a BMI of 21.5, then you’re in the middle of the normal range; 3 BMI points away from the underweight category and 3.5 BMI points away from the overweight category.
For this reason, a 21.5 BMI is greatly desired by a lot of people, even though it doesn’t guarantee optimal health. Still, someone with a BMI of 21.5 is unlikely to suffer from weight-related problems.
A 21.6 BMI is a good score in the sense that your weight is where it should be for your height. Whether or not a BMI of 21.6 is healthy depends on your body fat and muscle mass levels.
If you’ve got a 21.7 BMI, then you’re well within the healthy body weight range and have a much lower BMI than average. Obviously, some people who have a BMI of 21.7 may benefit from increasing their muscle strength.
A BMI of 21.8 means that your body weight is neither too low nor too high; it’s right on point. Some people who have a 21.8 BMI may need to improve their body composition, whereas others with the same BMI may already have sufficient quantities of muscle mass and body fat.
A BMI of 21.9 is fairly typical of those who have a slim build and a healthy weight for their height. With a 21.9 BMI, you’re 3 full BMI points away from the overweight category.
In conclusion: What does a BMI of 21 mean for your health?
As noted, a BMI of 21 is good in the sense that you don’t struggle with your weight, which is a problem for many people. For this reason, it seems plausible to say that those with a 21 BMI are likely to be healthier than average.
That said, it’s possible to be unhealthy with a BMI of 21 if you have too much body fat and comparatively little muscle mass.
In this scenario, you’d want to eat in a moderate calorie deficit to lose fat (ensuring that you get enough protein) while performing strength training to gain additional muscle mass.
Of course, some people who have a 21 BMI have plenty of muscle mass and not a whole lot of body fat.
This is the ideal physique to aim for from a physical health perspective because body fat can be a burden on your immune system and organs, whereas muscle mass, up to a point, can make your body more resilient.
- Kato, M., Shimazu, M., Moriguchi, S., & Kishino, Y. (1996). Body mass index (BMI) is a reliable index to estimate obesity as a risk factor for deteriorating health. The Tokushima journal of experimental medicine, 43(1-2), 1–6.