Obese, Skinny or Perfect; some things you might not know about genetics and obesity.
Ever wonder why the girl next door has a perfect figure but you never see her down the gym? Or why that bloke in the gym tells you he can eat what he wants and not put on any fat? Well there are many genetic reasons for why that might be. However just because I’m saying they are genetic and therefore foster the notion of a predisposition to either gain, lose or maintain weight that doesn’t mean you can give up entirely on achieving the healthy body you want. It just means that certain body types are harder to get from your biological starting point so don’t you dare start thinking, well if it’s genetic then why bother?
So who is obese and why is being overweight a problem you might ask? Where to start is a better question. Obesity is measured as a Body mass index (BMI) of ≥30.00 (kg/m2) as classified by the World Health Organisation. Further to this it is accounted for as an abnormal or extensive fat accumulation negatively affecting health. Simply put If you continue to overeat your adipose (fat) cells will get bigger, when they can’t get any bigger they multiply. At this point it is almost impossible to reduce cell numbers and it becomes easier to store fat. Your body might start to recognise the obese weight as the optimum weight and try to drag you back to it whatever you do. From a neurological point of view you will start to react to food when you’re consuming just enough and more than enough as if you are in constant starvation. This is the point you do not want to reach. As for why does it matter, it matters.
Obesity correlates strongly with high blood pressure and hypertension (Biscevic 2005) as a start, cancer mortality (Carroll 1998), physical obesity with the development of Sarcopenic obesity which is muscle impairment through fat infiltration (Stenholm 2008) and so much more. The economic cost to the tax payer is also immense with the obese population of the Great British public (yes that’s us) costing the NHS upwards of 2 billion pounds a year up until 2030 (NHS 2011). In addition there are more pharmaceuticals per person being prescribed as a factor of increasing BMI even after age, gender, smoking habits, living conditions, and education have been adjusted for (Ademi 2010). So why is this? I will now explain some of the reasons that I believe most people over look or at least do not understand correctly.
I mentioned a genetic predisposition being of paramount importance well this is true and arguably the defining factor as to who will ultimately become obese. Evidence for this can be seen across the lifespan and even as a racial trait. Undurti (2010) shows us that Pima Indians have a genetic predisposition to be obese due to a condition called hypothalamic dysfunction giving rise to an inability for the body to control functions via the pituitary gland. There is however a difference in the populations of that race when environment is taken into account however the Pima Indians are still by and large classified as obese. To give you a contrast 50% of Pima Indians suffer from type 2 diabetes (diabetes being a factor of energy dense foods, hypothalamic dysfunction and insulin response) and the Asian races only 5% (Habiba 2010).
That’s just the Pima Indians I hear you cry…. Well no it’s all of us, at least all of us have an optimum weight it just happens to be that some people are more at risk of being overweight naturally than others. Salans, Horton and Sims (1971) conducted a study using prisoners at Vermont state prison. They were instructed to gain 25% of their bodyweight through over feeding in exchange for an early release from prison. What was interesting was that putting on weight was more difficult for some than others. Some subjects managed the full extra 25% however others could not, even on 10,000 calories a day (that’s 2ooo short of what Micheal Phelps eats), they hit what is called a plateau. It seems from this reasonable to assert that individual differences play a part here on the genetic level. This is because the body identifies itself as having an optimal (preferred) weight and will always seek to bring you back to it. In my case I am naturally very thin and when I train in the gym and acquire new muscle mass it is very difficult to keep it especially if I fall ill and do not eat. An interesting note here is that an increase in muscle mass will increase your BMR and help you expend more calories so keep that in mind if you’re trying to lose fat.
Some lucky people simply have no desire to eat more than their body needs to survive. How much your body needs is your basal metabolic rate (BMR) based on a calculation taking into account age, sex, height, and weight. This is the amount of nutrition you need to live, for your heart to beat and your brain to function. These people have hormonal controls that can inhibit eating behaviour, let’s call them a protective measure. Carnell & Wardle (2009) illustrates this in Children with differing levels of satiety and attributes it to a genetic component in appetite called the FTO gene. Children were approached after having dinner and asked how full they felt, they were then set on a task (colouring, drawing etc) and plate of food placed beside them. Some children ate the full plate even those reporting that they felt full and others nothing at all. This eating behaviour can also be learnt from parents however interestingly the FTO gene was further confirmed to associate with obesity in adults and children which basically means if you have 1 or 2 copies of the allelomorph you are likely to weigh more than those who do not. Think of it this way, a snacking child is likely to be a snacking, potentially obese adult due to the FTO gene.
So we’ve covered racial traits, forced obesity and optimum weight and feeding behaviours based on genetics. Where confusion could arise here is in understanding the optimum weight in all this. You might think well if we are all supposed to be a constant weight why aren’t we? Well as I mentioned before Individual differences play a major part. We know that everyone is different and what’s more that some individual’s bodies can be better at coping than others. Whatever category you fall into, skinny, slim, perfect, overweight or obese it is your duty to yourself to find out how to be healthy. We don’t all need a six pack abdominal region but we should all at least try to be healthy for our own benefit, our family’s and the nation at large (no pun intended).
I hope you can see the convincing arguments there and if you don’t already, start to take care of yourself now you’re aware of them. A huge point I want to make here is that it’s not all negative. Just because you might be genetically predisposed to be overweight nothing is stopping you from making a positive lifestyle change for the better. It will take a monumental effort for some and no effort at all for others but it can be done.
Posted on January 16, 2012, in Fitness, Health, Psychology, Science and tagged appetite, fat, fit, Fitness, genetic, genetics, health, neuropsychology, obesity, sarcopenic, satiety, skinny, weight management. Bookmark the permalink. 5 Comments.