What is your body mass index (and is it an accurate measure of health)?

Body mass index (BMI) is an equation used to measure body fat. Your BMI is calculated by your weight in kilograms divided by your height in metres squared. From this calculation, you get a score which shows you where you sit on the weight spectrum. A high BMI is linked to obesity, whereas a very low BMI is linked to anorexia and malnutrition. However, your BMI isn't always an accurate representation of your overall health. This article will discuss everything you need to know about your BMI, and why it can sometimes be an inaccurate.

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BMI chart: what’s considered a normal body mass index?

As we mentioned above, BMI is widely used as a tool to assess if an individual is overweight or not. The following chart demonstrates how to determine whether your BMI falls within normal range:

Body Mass Index Chart

As a general rule, the BMI weight spectrum is as follows:

  • Any BMI below 18.5 is considered underweight
  • A BMI between 18.5 to 24.9 falls within normal range
  • A BMI between 25 to 29.9 is considered overweight
  • A BMI of 30 or higher is considered obese and at risk of health complications

Why BMI isn’t always an accurate way to measure health

BMI isn’t always the best measure to determine a person’s health - especially when it comes to athletic or extremely muscular body types. This is mainly because BMI doesn’t distinguish between fat and muscle. Someone whose weight consists mostly of muscle could potentially be considered obese if they only focused on their BMI. But, muscle is four times denser than fat - so now you can start to see the problem…

In fact, some people have a completely normal BMI and yet their waist circumference is well above the normal range, while other people are fit and healthy, and yet their BMI exceeds 25 - placing them in the “overweight” category.

A recent study found that close to half of Americans considered "overweight" by virtue of their BMIs (47.4 percent, or 34.4 million people) are healthy, as are 19.8 million who are considered "obese”.

Further findings also suggest that more than 30 percent of those with BMIs in the "normal" range - about 20.7 million people - are actually unhealthy based other health data. Additionally, more than two million people who are considered "very obese", by virtue of having a BMI of 35 or higher, are actually healthy.

Another factor to consider is your genetic makeup. It’s difficult to create a one-size-fits-all measurement for good health, as everyone is unique. Each of us have a different frame size (bone structure) and hold fat and muscle differently. Lifestyle also plays a huge role in overall health and wellbeing. All of these factors need to be considered together when measuring your health and fitness level.

Is weight gain and obesity genetic?

Obesity is linked to a combination of both genetic and environmental factors. You could have great genes and still become obese due to living an unhealthy lifestyle and vice versa, you could be genetically prone to obesity and successfully manage your weight through diet and exercise.

Genes related to weight gain

Research identified the FTO genotype as playing a role in weight gain as it affects your body’s sensitivity to saturated fat. Your level of fat intake and physical activity only modify the association with fat mass. This means that even if you are eating healthy and working out, what you eat can make you appear to carry more weight than others, even if you are actually healthier than other people.

In addition, FTO genotype may modify the association between physical activity and cardiovascular mortality. Another study looked at the FTO gene and explains that homozygous participants for the FTO-risk allele had a higher mean BMI than the other genotypes only when they had a high-saturated fat intake.

Nature vs nurture: the relationship between environment and genetics

It’s crucial to take into account the relationship between both your environment and your genetics. 

Environmental factors include:

  • Physical activity
  • Eating habits 
  • Whether you smoke or drink alcohol

Genetic factors include

  • Family history of obesity
  • Response to saturated fats and carbohydrates
  • Disease risk

In a bid to promote long-term, sustainable health, DNAFit have made it our mission to educate people about the importance of a personalised approach to diet and exercise. Understanding your body from a holistic point of view will help you overcome any problems you encounter when it comes to reaching your weight loss goals. 

By simply looking in the mirror and checking how you feel every day you can help you ascertain whether you are healthy or not. “Healthy” doesn’t mean having ripped abs or a toned physique like the models in magazines. If you eat a balanced diet that is in line with your genes and work out regularly to stay fit and active, you will already be taking the necessary steps to meet your goals. 

Download our ebook, The Ultimate Guide to Healthy Weight Loss, for some expert tips from our dietitians and sports scientists to help you reach your weight loss goals.

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