What Is the Difference Between BMR and BMI?

When you start becoming more concerned about your health, you may start to do more research about the science of metabolism, weight gain, muscle mass, and all the other related concepts. It may seem fairly easy to understand at first, but you’ll eventually run into a handful of abbreviations. Two of the most commonly confused abbreviations are BMR and BMI.

Since BMR and BMI are closely related, you may encounter them when you do your research. To help you differentiate the two, here are a few key concepts about BMR and BMI to clear up any confusion.

BMR = Basal Metabolic Rate

BMR is the number of calories your body burns and turns into energy each day to maintain your normal bodily functions while you’re at rest (ideally after waking). These calories go towards maintaining your body temperature, blood pressure, metabolism, brain function, and more. While you may not feel these functions, they’re all happening within your body to keep you alive and well.

You can compute for your Basal Metabolic Rate using a BMR calculator.

BMI = Body Mass Index

BMI is the ratio between your weight in kilograms and your height in centimetres. This ratio is commonly used to assess whether a person is within a healthy weight range. You can compute for your Body Mass Index using a BMI calculator.

Factors that Affect BMR

Your BMR is affected by a number of different factors. Like BMI, height and weight are important factors. However, body composition, age, climate, and any illnesses can also affect your BMR. 

Generally, the more muscle mass you have, the higher your BMR since your body requires more calories to maintain muscle. The older you are, the lower your BMR because older people tend to lose muscle mass and have a slower metabolism. If you live in extreme climates, you may have a higher BMR since your body works harder to maintain an average temperature. Lastly, if you have an illness or an injury, you have a higher BMR because your body works harder to heal itself.

Factors that Affect BMI

You need two variables to compute a person’s BMI: height and weight. However, keep in mind that BMI doesn’t factor in one’s body fat to muscle mass ratio. That’s why there are a few exceptions when it comes to using BMI to determine one’s health.

For one, people who have a lot of muscle mass may have a higher BMI. However, they are not considered overweight because of the ratio between their body fat and muscle mass. 

While a person’s height is required to measure their BMI, those who are very tall (over 190 centimetres) or very short (less than 150 centimetres) tend to have skewed results. The BMI scale tends to overestimate obesity in shorter people while underestimating it in taller people.

Lastly, ethnicity and gender also come into play. Some ethnicities either tend to store more body fat or they have a stockier build. Likewise, women tend to store more body fat. Their BMIs tend to be skewed to reflect their predisposition.

A Healthy BMR

The healthy BMR for women is at 1200-1600 calories a day. For men, it’s at 1600-2000 calories a day. Keep in mind that a lot of different factors affect BMR, so it’s hard to place a number on what’s considered “ideal.” This is unlike BMI, which has a chart that you can use to check whether or not you’re in the healthy range.

A Healthy BMI

There are several BMI charts to help you check whether you’re underweight, of normal weight, overweight, or obese. However, there isn’t a single chart that fits everyone. Your BMI changes as you age, so children, adolescents, adults, and the elderly have their own BMI charts. Likewise, one’s ethnicity and lean muscle mass can skew the chart in a different direction. Even men and women have different BMI charts.

This isn’t to say it’s impossible to learn whether or not your BMI is normal. Once you’ve used the BMI calculator to find your ratio, you can pick out a chart that caters to your age, gender, ethnicity, and even body mass. This will help you see if you’re within the healthy BMI range or not.