I’d like to use this post to introduce a very simple, and important, concept that is a key idea to understanding metabolic health: the “personal fat threshold.”
To give a simplified, high-level view of this concept, it’s helpful to envision your body as having two “compartments” in which to store fat. The first is the subcutaneous compartment. This is fat that is stored directly underneath the skin, for example on the arms, abdomen, or buttocks. This is the fat that we can visibly see, and that many people hate for aesthetic reasons.
The other compartment is the “ectopic” compartment. Ectopic fat includes “visceral fat” (fat surrounding important organs such as the kidneys and liver) as well as fat that is implanted inside of crucial organs such as the pancreas, the liver, the heart, and the muscles. Ectopic fat is not visible from the outside, but it leads to health problems such as heart disease, cancer, and diabetes.
The personal fat threshold is the concept that due to a variety of factors – primarily genetics, but also things like your childhood experiences and your gut microbiome – each of us has a different capacity to store fat in each of these compartments. Let’s imagine a few hypothetical people to make this point clear.
Imagine that each of the following people start out with zero fat on their body, but over time start gaining fat:
Al gains 10 pounds of subcutaneous fat. After this, he is no longer able to “build” any more subcutaneous fat, so he starts putting on ectopic fat. After gaining 5 pounds of ectopic fat, his body can no longer easily handle any further fat deposition, and accordingly he begins to experience a “metabolic breakdown” in which he has steep rises in his blood glucose, his blood pressure, his triglycerides, etc. As a result, he dies young of cardiac disease. Thus, it only takes a gain of 15 pounds of fat to make Al very metabolically ill. Al is what doctors call a “TOFI” – Thin on the Outside, Fat on the Inside, and is “metabolically fat,” even though he doesn’t really appear to be overweight.
Bob has a much greater “personal fat threshold.” His body is capable of storing up to 100 pounds of subcutaneous fat before there is significant “spillover” into the ectopic compartment. So even after gaining 80 pounds, Bob has little ectopic fat, and remains metabolically healthy, despite appearing to be quite obese.
Carl is an in-between of the two individuals above. He has the capacity to store 50 pounds of subcutaneous fat before experiencing significant ectopic fat deposition. So if Carl gains 80 pounds he will both appear to be grossly overweight, and in fact also have a lot of ectopic fat and the resultant health complications of type 2 diabetes, hypertension, high triglycerides, etc.
In other words, the personal fat threshold is simply the recognition that everybody has a certain amount of fat they can gain before they begin to experience health complications, and that this amount can vary widely between two individuals. Though this may seem like a fairly obvious point, it’s really worth understanding, because it sheds light on a number of well known points.
Consider that all of the following phenomena can be explained by the personal fat threshold:
Some individuals can develop severe type 2 diabetes despite not being. obviously overweight. Moreover, this tendency is particularly common in South Asian populations due to genetics. India, for example, has some of the highest rates of diabetes and heart disease on earth, despite not having particularly high rates of obesity.
Some people can live long, disease free, lives, despite being extremely obese.
The personal fat threshold was in large part developed by Dr. Roy Taylor, an English endocrinologist. You can watch this clip of Dr. Taylor being interviewed for further information about this concept:
