Here we go… I have started another massive online open course (MOOC) and I think I might be addicted. This new one is from Johns Hopkins University and is taking a systems science approach to the global obesity epidemic. Rather than see it as a problem of an obese individual, it is looking at it as a problem of society as a whole. The shift in weight has happened right across society, even the thin people are fatter than they used to be! Are you listening Cancer Research UK? Spotted in a London tube station (well you could hardly miss it)
One of the things we often struggle with when trying to lose weight is that after a while it we simply stop losing it. Our body hangs on to the fat. We can’t understand it because we are eating fewer calories and exercising more so surely if the calories going into our body are fewer than the calories going out in energy burn, we will lose weight? Just like a bank account, if we put in less than we spend the balance will go down (seriously, I know that to be true!). Prof. Tom Glass from Johns Hopkins sums up the Calories on/Calories out theory beautifully in this slide:
Basically you can do four things with the calories you eat. You can burn them for fuel; use them to build stuff: waste them; or store them as fat. It doesn’t matter what kind of calorie they are, your body simply decides and decides the same way constantly, whatever. Obesity then inevitably occurs when the burning and the using of the calories does not equal or exceed the consumption. We store the excess as fat. But our bodies are not a bank account, the human body is a complex metabolic factory and its treasure is fat. The partitioning of calories is subject to hormonal signalling and fat is not an inert tissue! It is biologically active. Fat (adipose tissue) can increase insulin release into the blood stream which instructs the body to store energy (not just excess energy but ANY energy) fat. The partitioning system also responds to the type of food we eat. Carbohydrate intake also raises our insulin levels that, guess what, instructs our bodies to store fat (eating fat, by the way, doesn’t). And just so we understand how elegant this system is, insulin starts to rise before the food is even in your mouth. Sit next to someone on the train eating sweet porridge and you start secreting more insulin and that’s not an good feeling. I know that from experience!
So a better illustration of what is going on is shown in this slide also from Prof. Tom Glass:
Front and centre of the problem is the partitioning system, choosing to use or store calories based on the signalling it is getting from the food we eat and the metabolic state of our bodies. The more carbohydrate we eat, and unfortunately, the fatter we are, the more energy we will store as fat rather than use for fuel. This is the function of a single hormone and there are many hormonal interactions in reality.
The ability of human beings to store fat (I have never seen a fat buzzard) is an evolutionary genetic triumph that has made us the successful species we are. Its a tragedy that modern food has turned it it an evolutionary disaster that is reversing medical gains and is now starting actually to shorten human life expectancy.