How to Lower Your BMI

In the early 1800s, Belgian mathematician Adolphe Quetelet sought to understand the distribution of physical characteristics of the “average man” and “average woman”. To do this, he developed a formula, dividing weight (kg) by height (m^2), and sought to determine if the corresponding number could predict health risks.

By the 1970s, researchers began to use the formula as a simple method to categorize individuals by body mass and associated health outcomes. It was during this period that the term "Body Mass Index" (BMI) became more common.

The World Health Organization and other health organizations use BMI to classify individuals into categories:

• Underweight: BMI < 18.5
• Normal weight: BMI 18.5–24.9
• Overweight: BMI 25–29.9
• Obese: BMI ≥ 30some text
  • Class I (Moderate obesity): BMI 30–34.9
  • Class II (Severe obesity): BMI 35–39.9
  • Class III (Morbid or Extreme obesity): BMI ≥40
    

There are benefits and limitations to the use of Body Mass Index. In this article, we’ll dive into these and answer questions like: why is my BMI so high? How much weight do I need to lose to lower my BMI? What is the best exercise to reduce BMI? 

Benefits of BMI

BMI can be useful as a series of loose guidelines for overall health risk. It has the advantage of accessibility, since it is easy to calculate, and it provides a standardized method for comparing individuals across different populations and demographics. However, because of its limitations,  BMI is perhaps best understood as a way of identifying trends in weight-related health conditions at a large scale… not as a steadfast formula to determine an individual’s health. 

Limitations of BMI and why it’s a flawed metric

BMI can be a useful tool at the population level, allowing for the comparison of weight status across different populations over time. This standardization facilitates public health monitoring and the identification of trends in overweight and obesity rates. That said,  it often fails at the individual level because it doesn’t differentiate between muscle and fat mass, nor does it account for the distribution of fat in the body. This can lead to misleading classifications, especially in athletes and individuals with high muscle mass or those with central obesity. 

For instance, a 5'10" college football player weighing 258 pounds has a BMI of 37, classifying him as severely obese by BMI standards. However, any reasonable person would question this conclusion due to the athlete’s significant muscle mass, highlighting that BMI cannot accurately predict weight-related health risks in such cases.

Now let’s look at the other end of the spectrum. A 5'2", 54-year-old woman weighing 123 pounds  has a BMI of 22, classifying her as normal weight. However, most of her body fat is concentrated in her abdomen, with her arms and legs remaining quite lean. Based solely on her BMI, she would be considered low risk for weight-related health issues. However, her abdominal fat distribution places her at risk for insulin resistance, type 2 diabetes, and cardiovascular disease.

These examples outline the potential flaws of BMI and the importance of using it in conjunction with other assessments and measurements for a more comprehensive understanding of an individual's health.

What to focus on instead of BMI

When it comes to overall health, it is important to focus on metabolic health rather than just body weight. A potential alternative to BMI is called the triglyceride / HDL ratio. This is calculated by dividing triglyceride level by HDLc level. Higher ratios indicate greater risk of metabolic syndrome.

Reiterating the point above, an individual could be categorically obese but in great metabolic health, while someone else could be considered normal weight and metabolically unhealthy. When we switch our focus to metabolic health, weight may move to the back burner to make room for other markers like glucose control, blood lipid levels, and blood pressure. Equally important are energy levels, self confidence, and the ability to perform daily tasks independently.

Consider exercise as an example. If you work out solely to reduce your BMI to an arbitrary number on a chart, rather than because it makes you feel good, you’re unlikely to maintain this healthy habit long-term. This approach doesn't focus on improving your quality of life. Similarly, if you aim to lose weight just to lower your BMI, you’re overlooking the bigger picture and assessing your health through a flawed lens.

The Takeaway 

When it comes to achieving your metabolic health goals, losing weight is important, but it's not the sole factor in overall health (and as we’ve learned, neither is BMI). It's the changes to your diet and lifestyle that lead to better health, with weight loss often being a positive side effect of those improvements.

Virta helps members achieve better metabolic health with the transformative power of nutrition, guided by an expert care team and technology tailored to individual preferences and goals. Many members join Virta to lose weight, but what they get in return–more energy, greater vitality, and the ability to do the things they love with the people they love–is so much more. See if you’re eligible for Virta Health here.