In order to understand diabetes one needs to consider the normal physiological role of insulin and glucose in the transport of carbohydrate around the body. Nerve cells in the brain, spinal cord and elsewhere always take as much glucose from the blood as they need. Carbohydrates are the real brain food. Other tissues, particularly muscle cells and fat cells, only take glucose from the blood when directed to, by the hormone insulin. Insulin can be likened to a key that fits into a lock and opens the door for glucose to enter the cell. The lock is the insulin receptor which straddles the surface membrane of the cell and the door is the set of proteins which actively transport glucose into the cell. This door also has a security chain to keep out additional glucose when the house is full, the house being the cell in this analogy. As a cell become fully loaded with energy from both glucose and fats it becomes increasing resistant to insulin, and ever higher concentrations of insulin are required to coax it to take in that extra little bit of glucose.
Muscle is a metabolically active tissue and typically makes up half of our body weight, making it the number one player in glucose/insulin metabolism and diabetes. It is fairly well accepted that the build-up of fat globules (intramyocellular lipid) within the muscle cells is the main factor that causes them to become resistant to insulin. The fat you eat is not only the fat you wear but also the fat that clogs your muscle cells. To put this in terms of the insulin lock and key analogy, fat in the muscle cell is the gum that stops the insulin key from fitting into the lock. There are two ways that we can ungum our muscle cells: exercise and a low fat plant-based diet. Exercise simply burns off the muscle stores of both fat and glucose. A low fat, plant-based diet prevents the muscle cells from becoming overladen with fat.
There are factors outside the cell that can make the insulin receptor more resistant to insulin. Perhaps they could be keyhole covers in the lock and key analogy. These include, saturated fat, stress hormones and inflammatory mediators. The saturated fat comes from a diet rich in meat, dairy, eggs and processed foods. The stress hormone cortisone is increased by both physical and psychological stressors. Dietary fats, animal protein and several inflammatory substances in meat cause an acute rise in blood levels of cytokines and other inflammatory mediators. Abdominal fat produces its own inflammatory mediators. A low fat plant-based diet minimises saturated fat intake and reduces inflammation.
The gut microbiome can help protect us against insulin resistance and type 2 diabetes. The bacteria in the colon that help us to digest resistant starch and other forms of dietary fibre release short chain fatty acids (SFAs) such as butyrate. These SFAs regulate carbohydrate metabolism, reducing insulin resistance and protecting against the development of diabetes.
Let us consider what happens if we keep shovelling fats and other concentrated calories into our bodies beyond our needs. The whole system becomes overloaded with glucose and oils and the cells all over the body become insulin resistant. Insulin resistance is what cells are meant to do when they don’t need any more glucose – it’s a normal response, which protects cells from becoming overloaded with energy substrates, while leaving more glucose available for the cells that do need it. With insulin resistance happening all over the body, there is nowhere for the glucose in the blood to go, and glucose levels spiral out of control despite maximum production of insulin – this scenario is type 2 diabetes.
Some people have fat cells that are willing to just keep taking in glucose and fats and getting bigger and bigger to morbidly obese levels, and this may hold back diabetes, but most of us have fat cells that take the more sensible approach of saying no more by becoming insulin resistant. Obesity was not a useful survival trait for hunter-gatherers – nor any other species for that matter.
Low carbohydrate diets are a quick fix for diabetes. The underlying problem of insulin resistance is dealt with by simply cutting off the main supply line for blood glucose, dietary carbohydrate. Unfortunately low carbohydrate diets are high in fat, animal protein, and usually of high energy density. They maintain the body in a permanent state of energy overload and insulin resistance. They also increase the risk of the number one killer in diabetes – heart disease.
Type 2 diabetes can eventually become irreversible. The insulin producing cells of the pancreas initially work very hard to make as much insulin as they can, often many times the normal amount. Eventually these cells can become damaged, producing less insulin, and as a result blood glucose levels rise and diabetes gets worse. Even at this late stage, a whole foods plant based diet will improve insulin sensitivity.