I recently listened to the audiobook Why we eat too much by Andrew Jenkinson.
Andrew is a bariatirc surgeon who has been treating people with obesity for some time and has set out to answer why people become obese and also why people struggle to loose weight.
This was one of the best books I have listened to and really gives a comprehensive and indepth understanding of how the human body has become so adapted to regulate weight and the amount of fat we store.
Andrew also uses analogies and stories to explain makes it very easy to understand.
Here is a summary mind map of the complete regualtion process.
The weight set point theory states that there is a set point in the hypothalamus (part of the brain responsible for regulatory function) that determines the amount of fat we store. This setpoint is influenced by a number of factors and can increase or decrease over time.
Weight set point is infucenced by
- Genetics and Epigenetics- there are genes that predispose a person to store more fat so if you originate from a history where food was limited then you will probably have more of a propensity to store fat. Epigenetics, a more recent term is the process by which certain genes can be activated or deactivated due to environmental changes which are then passed on to offspring. For example, if the mother is pregnant in an environment where food is of low-calorie density then the foetus will activate genes to store fat. As the foetus then is born and goes on to have children the children inherit these changes even though the children may live in a completely different environment. This does explain to a degree why increase levels of obesity in 2nd and 3rd generation immigrants whose grandparents migrated from environments of low-calorie food to a more westernised high calorie high refined carbohydrate environment.
- The body can increase or decrease the basal metabolic rate according to the number of calories consumed. If the calorie intake drops, as in a diet, then BMR is reduced and continues to stay low and when calories increase as BMR is low leads to a faster rate of fat storage.
- The amount of fat already stored- Fat cells produce the hormone Leptin which acts as negative feedback on the hypothalamus indicating that they are full. At a certain point, the hypothalamus can become Leptin resistant and stop responding to leptin and so fat storage increases. Insulin which is produced when we eat carbohydrates can increase leptin resistance. The increase in fat levels then causes the production of TNF an inflammatory signal causing the increase in fat storage.
- Stress- the sympathetic and parasympathetic systems cause the production of adrenal hormones as required in a state of chronic stress there are increased levels of cortisol produced by the adrenal glands and this results in increased fat storage. This can lead to a Cushingoid syndrome type appearance i.e moon face and fat around the abdomen.
- stomach and intestines – produce ghrelin and also peptide XX which indicate if the stomach is empty or full and this sends a signal to make us consume either more or less food.
- Insulin- produced in the pancreas in response to high blood sugar levels and causes the storage of glycogen in the muscles and also acts on the liver. Blood sugar is kept to approx 5g of sugar in 5 litres of blood (one teaspoon).
- Omega 3 and omega 6- essential fatty acids required by the body for function. Omega 3 integrates into the cell membrane and keeps the cell membranes flexible. Omega 6 is less flexible and causes the cell membrane to become more rigid. A diet of 3 to 1 omega 3 to omega 6 is ideal. The western diet contains high levels of Omega 6 and this has the result in causing inflammation increased fat storage. Omega 6 also causes the release of cannabinoids in the brain resulting in a stupor effect post eating.
- The amount of saturated fat eaten doesn’t seem to impact the amount of fat stored the other factors above seem to have far more influence.
- The western diet of highly refined carbohydrates and low levels of fat and higher levels of trans fat is leading to increasing levels of obesity
main advice
Eat less refined sugar and in lower freqency and less transfats and a diet with more protien and saturated fat. Sleep well and mediitate to reduce stress.