Rethinking Fat: Body Composition, Visceral Fat, and Other Metrics to Measure

Firstly, the term obese is most commonly used in conjunction with Body Mass Index (BMI). The BMI measure is a very simple calculation: your total weight in kilograms, divided by the square of your height in meters. But what is weight here? On this scale, the weight of our muscles, our blood, our organs, and indeed our  bones are all lumped together with the weight of our fat, and assessed together to give us an assessment of our health. But anyone who has trained with weights, or has physical work, anyone who is naturally broad across the shoulders, many non-white ethnic groups, or indeed anyone who is shorter than average will have a BMI which doesn’t really reflect their true state of health.

 

Further, BMI can grossly misjudge someone as healthy, who may have lower than average muscle mass or someone who, through lifestyle factors we will get into later, has what little fat they have in the wrong place – i.e., around their organs. These factors may lead a doctor to send someone away thinking they have nothing to do to improve their health from a weight/composition point of view, but they would be very wrong. Weight alone isn’t an accurate measure of a person’s health – it fails to take into account a person’s body composition, health markers such as cholesterol and blood sugar, behaviours, and more.

 

These problems and limitations with using BMI as a measure of health are well known. BMI is widely acknowledged as a terrible way to measure and talk about weight and composition. So, why is it still used? Simply put, BMI is easily reproducible. Any doctor, without much equipment, can weigh someone, and measure their height. This makes BMI a quick, easy, and reproducible metric to use.

With that in mind, the first reason we never use the o-word at My Vital Metrics is because it’s most commonly used in conjunction with BMI. Rather than talk to you about your BMI, we prefer to take a broader perspective on your health and fitness by considering a range of health markers. 

However, some studies have also applied the o-word to body fat measures. They have selected a range of body fats and determined that figures above that range are considered ‘obese’. As the DEXA scan we use, as the gold standard in body composition analysis, does indeed give you a body fat percentage, you might think that for certain clients who fall above that range, we would apply the o-word moniker to them. Once again, we definitely do not.

As soon as you apply the o-word, the instant response or reaction is the thought that the solution is to lose weight, but this is not always the case. Just as a BMI hides any information about composition (how much muscle, bone and fat there is) even a body fat percentage hides information about the two factors which make it up. a Body fat percentage is Total Mass of fat, divided by the total mass. But what if the total mass of fat is low, but the total mass (which includes the muscle and bone) is also very low. For example, someone who has very light or thin  bones, and low muscle mass. Their body fat percentage my come up high, but this is no reason to think that the best plan for them will be to lose weight, or  lose fat. A more appropriate plan may be to try to raise muscle mass and support a healthy metabolism Muscle, when put to use, acts as a furnace for burning fat, and low amounts of it may make efforts to lose fat very difficult.

Finally, in contrast, a person’s body fat percentage may be low, but when we look at their visceral fat – this is the fat that sits around their  organs, we might find that it is  high.  Just 500g of this  fat, in the wrong place, can  have an adverse effect on a persons overall health, and it doesn’t always correspond to overall levels of body fat, or indeed necessarily with an unhealthy lifestyle. Excessive stress, or disrupted sleep patterns over  a longer period of time may lead to high visceral fat levels. If this is the case, then whatever percentage of fat exists in the  rest of the body, the person may struggle to achieve overall  health.

So there’s the first two reasons we never use the o-word. It is not a good or useful term, and doesn’t help us at all get to a plan of action.

There’s one final reason we don’t use the term, and that  is that it has become a term which for many people is weighed down with feelings of shame. From the schoolyard to the doctors office, the o-word has been used to attempt to shame people into some sort of compliance. But whether well-intentioned or cruel, that shame has consistently failed, and I  believe, will always consistently  fail to enact or inspire any real or lasting change in someone. Usually the term leaves people feeling worse than before, when we need them to feel positive and empowered to make the changes without the fear or shame hanging over them.