BMI: What You Need to Know


If you live with type 2 type diabetes (T2D), you know that there’s a lot that goes into taking care of your health. Managing T2D  often includes not only a medication regimen, but also being mindful of your diet, exercising regularly, and may include managing your weight.

If weight management is a part of your diabetes care plan, you’ve likely heard of body mass index, or BMI. You may be wondering, isn’t BMI an outdated metric (it’s been around for nearly 200 years!), and is it relevant to my weight management goals? 

BMI is a measure of body fat based on height and weight that applies to adult men and women. It’s been used for a long time—it was created by a Belgian mathematician in 1832. Even though our understanding of health has evolved a lot since the invention of BMI, It’s since been used by millions of people and providers and sticks around as a frequently-used measurement of physical health.

What is BMI?

BMI is a metric used to calculate a body fat estimate.

You can easily calculate it here. The equation is: BMI = (weight (lbs) / height (in)) x 703.

Since weight management is usually an important component of diabetes management, knowing your body fat through the lens of BMI can be an important key to knowing your overall health. 

It’s important to frame this for what it is: an estimate. Measuring body fat takes more sophisticated technology—a digital body fat analyzer—which can be expensive and inaccessible for many. BMI, therefore, is used as a stand-in. 

BMI categories are as followed:

  • <18.5 = underweight 
  • 18.5–24.9 = normal weight
  • 25–29.9 = overweight
  • 30 or greater = obese 

BMI: What it can and cannot measure

BMI can be a good indicator for estimating risk for certain conditions, such as some cancers, hypertension, gallstones, breathing issues and malnutrition. 

While high or low weight is not the cause of any one of those conditions, BMI can act as a starting point for healthcare providers to assess risk for conditions that are more common in people who are either severely underweight or overweight or /obese

However, many experts feel that the measure is outdated and doesn’t account for several more relevant metrics that relate to physical health.

In fact, BMI isn’t a very accurate way to measure body fat and doesn’t account for body type or even the amount of muscle you may have (referred to as body composition). 

Many elite athletes have high BMIs that would categorize them as “unhealthy” or falsely at risk for certain diseases—and BMI certainly doesn’t measure one’s athletic ability! 

BMI is not a perfect measure of health. 

While some healthcare providers have replaced BMI with more personalized or holistic measures of health; when it is used, it’s just one tool for assessing health-related goals. 

The limits of measuring BMI

South Carolina-based therapist and certified diabetes educator Alexis Skelley thinks people with diabetes need to keep things simple when it comes to managing their weight. 

In her practice, she coaches people with diabetes pursuing weight loss and her focus is on getting “back to the basics.”

BMI can be a useful tool from a clinical standpoint, Skelley said, but for individual patients, the numbers can be harmful to mental health, leading to frustration, disappointment and even depressive thoughts. 

She doesn’t see BMI as a number her clients should be concerned with.

BMI doesn’t measure muscle mass, which can lead to false high readings. As technology improves, clinicians can hone in on more useful metrics, such as fat mass versus fat-free mass and visceral fat, which are more relevant to assessing health-related risks. 

“Even with weight, pay more attention to the things that affect your weight versus the number itself. The number won’t do anything for you,” Skelley said. “Paying more attention to how you feel, how your clothes fit, what you’re eating, how you’re sleeping, how often you’re moving, etc.” 

BMI and your weight loss plan

Weight management is complex. While BMI may have a place in your weight management plan and defining your goals, Skelley suggests focusing on those other indicators of physical wellness.


Getting enough sleep is crucial to all areas of health! If you’re trying to lose weight but you’re sleep deprived, your efforts will be tanked. Insufficient sleep affects the hormones that control appetite, such as ghrelin and leptin. 

Additionally, insulin resistance skyrockets if you’re chronically sleep-deprived, which can work against your weight management goals. Aim for between 7–9 hours per night, ideally.


Stress can cause us to crave carbohydrates and sugar, which can lead to weight gain. Stress also causes full-body inflammation and insulin resistance. 

Managing stress through things like yoga, meditation, support groups and breathing exercises will not only support your weight management goals, but it can improve your quality of life as well. 

Focus on nutritious and filling foods

With diabetes, you may feel a sense of security being able to see the number of carbohydrates on a nutrition label, but it can be healthier (and more filling) to eat something that doesn’t come in a package. 

When you eat whole foods like fruits, vegetables, nuts and grains, you may find yourself focusing less on counting calories. Fiber-rich foods can help you feel full more quickly and more satisfied. 


Physical activity has many health benefits. It is a natural antidepressant and is great for energy and mental health. However, an exercise routine can be overwhelming. 

Adapt it to your needs and circumstances. Something as simple as a walk can return benefits for weight and blood sugar levels, blood pressure, stress, mood and sleep. 

In fact, positive changes in exercise and diet can greatly benefit your heart and metabolic health (including T2D), regardless of whether or not it accompanies weight loss.

Keep it in perspective

Weight management and T2D can be a lot to manage day in and day out. If weight loss is a goal for your health and diabetes care, it can be easy to fixate on numbers like BMI. Focusing on only one metric, such as body fat or even the number on the scale, may not be helpful nor give you an overall picture of your health. 

While BMI can be helpful as a benchmark, incorporating other factors—such as how you’re sleeping and managing stress, getting regular physical activity and eating nutritious and less-processed foods—may be a better way to assess your progress toward diabetes-related goals. 

Skelley offered a reminder to anyone looking to make lifestyle changes to support their T2D: “Simple doesn’t always mean easy, but it is worth it.” Yes, it is!

Editor’s note: Educational content related to weight management is made possible with support from Lilly, an active partner of Beyond Type 2 at the time of publication. Editorial control rests solely on Beyond Type 2.

Written By Christine Fallabel , Posted , Updated 09/01/23

Christine Fallabel has been living with type 1 diabetes since 2000. She's a health and science writer and has been featured in Diabetes Daily Grind, diaTribe, Insulin Nation and Diabetics Doing Things, and is a regular contributor to Diabetes Strong and Healthline. She earned her Master of Public Health from Temple University. In her spare time, she enjoys hiking with her husband in the mountains of Colorado, tinkering with her DIY Loop insulin pump, coffee and reading in front of a cozy fire.