Ask yourself this question. If you had to choose between being thin without having to do any exercise, or doing lots of exercise but still have a high BMI, which would you choose? Silly question I know, undoubtedly most people will opt for the former. But after reading this blog see whether you have a different opinion.
We all know someone who seems to have no problems with their weight. No matter what they eat, or how little exercise they do, they are slim and in shape. You may even be this person. On the other hand, we may know people who seem on the larger side but are brilliant at a sport or fitter than you could ever hope to be. In fact, fitness and fatness aren’t as closely linked as we once thought. In addition, newer understanding about where we store fat may actually prove to be the most important factor.
People often change their lifestyle and exercise levels as a reactive measure. The classic example is putting weight on during the festive season, and then stepping up the exercise in the new year. However, science is increasingly telling us that there is actually very little correlation between our size and our overall health and fitness. Some studies suggest that the risk of cardiovascular disease is lower in individuals with a high BMI and good aerobic fitness, compared with individuals with normal BMI and poor fitness (1).
In addition to this, the way our body distributes fat can hold more significance in how damaging it is to our health. Fat that is more centrally placed (sometimes described as being apple shaped) is potentially much more harmful than more peripherally distributed fat. Central fat is often accompanied by fat around our organs (visceral fat) and within the abdominal cavity. You may have heard the term ‘fatty liver’ before. Ironically, it is possible to have large stores of visceral fat but low levels of fat below the skin (subcutaneous fat). This will give you the appearance of a TOFI, thin on the outside, fat on the inside.
Why does central obesity matter?
In medical terms, this type of obesity epidemic is called ‘central obesity’. There are very strong links with central obesity and developing the Metabolic Syndrome. The metabolic syndrome is a cluster of biochemical and physiological abnormalities that are associated with the development of cardiovascular disease, insulin resistance and type 2 diabetes. Not good news at all.
Are genetic factors important with central fat?
I often hear patients blame their genetics for being overweight, saying ‘big bones run in the family’. This may even affect their willingness to try and lose weight as they feel it is a battle they are destined to lose. When it comes to losing subcutaneous fat, for most people, there is no reason why it can't be lost. There are however associated genetic traits that make this more difficult e.g. a large appetite, variations in metabolism. But very rarely are genetics the primary cause of obesity (Prader-Willi syndrome is one example of a rare genetic condition that makes you put on weight). In many cases, obesity is more to do with environmental factors, such as poor eating habits learned during childhood.
On the other hand, when it comes to central obesity some studies suggest that genetics play a much bigger role and the majority of inter-subject variance in central abdominal fat in non-obese individuals is due to genetic factors (2). There may also be a variation across different ethnic backgrounds. People of a South Asian origin have a more centralised distribution of body fat without necessarily developing generalised obesity and show raised obesity-related risk at lower waist circumference levels (3).
How do we measure internal fat?
If you wish to spend your hard earned money measuring your internal fat a common technique used is bioelectrical impedance analysis (BIA) machine. You might find this machine at the gym or specialist sports clinics. This machine passes an electrical current through the body to calculate the percentage of body fat. Unfortunatley, there are lots of inaccuracies associated with this method. Dehydration, for example, affects BIA measurements as it causes an increase in the body's electrical resistance. Also, the jury is out on how accurately it can differentiate between internal and subcutaneous fat. New medical imaging techniques using MRI and CT are now allowing us to measure internal fat accurately. But these techniques are still mainly used for research purposes only.
Can we reduce central obesity and internal fat?
Yes, you guessed it. Diet and exercise come to the rescue once again. However, to target central and visceral fatty deposits, we need to be smart about how we exercise. Some studies suggest that light aerobic exercise is relatively ineffective at targeting central obesity. In contrast, anaerobic, or high intensity exercise depletes our muscle glycogen stores and requires the mobilisation of our fat stores from within the body. There is some evidence to also suggest that early morning exercise before eating carbohydrates help us to deplete our glycogen stores and burn that internal fat. Diet also plays an important part in reducing visceral fat. This includes avoiding refined sugar and carbohydrates and increasing our fibre content (fibre-facts-and-fibs.html).
TOFI vs. SUMO
Lets look at the life of a sumo wrestler. They are the experts in high intensity exercise, or interval training as they perform explosive bouts of movement followed by short periods of rest. If you were to look at a sumos’ body composition by putting them through a MRI scanner, amazingly they would demonstrate very little internal fat. They would also have an extremely good anaerobic capacity and very high fitness levels. All this despite the fact that some wrestlers can reach a BMI of 50+ and consume over 6000 calories a day. Sumos also have large amounts of muscle mass which helps increase their metabolism burning those stores of fat around their organs (gain-mass-to-lose-weight.html). In contrast, our skinny friend who does no exercise may display very poor fitness, low muscle mass, and high levels of central obesity, despite appearing thin and healthy on the outside.
What does this mean for me?
The message i'm trying to get across from this blog is not to judge fitness on appearance. And also not to be complacent and think that just because you might not be overweight you should neglect your fitness. Not many of us will ever get the opportunity to formally measure our central fat stores, just like we won’t get the chance to measure the state of our arteries (and if ever you do, it’s probably a bit too late!). However, by incorporating high intensity interval sessions like a sumo wrestler does, we can improve our anaerobic threshold and burn our internal fat stores, reducing the risk of developing type 2 diabetes and cardiovascular disease. A good way to start doing this is by mixing up your running! (smart-running-ways-to-train.html).
In summary, it is much better to treat our bodies with respect both on the inside and out, and not get obsessed with appearance and waistlines!