Stubborn fat develops in as person when its hormonal pathways are broken down. Age does play a role in this due to the facts that fat deposits increase and become more resistant to fat loss methods as people get older.
This a phenomenon people can not control, but some things that lead to stubborn fat development can be somehow controlled. Losing weight on crash diets and then regaining it—often known as the “rebound effect”—only increase stubborn fat on long term. A decrease in exercise and activity level also compounds the stubborn fat problem. This is why people who crash-diet on low calories and refuse to exercise often have the worst stubborn fat problems of all.
Our ancestors really never had to deal with this dilemma because they moved and engaged in physical labor as a normal part of daily life, whereas technological conveniences and the modern way of life have caused many of us to become indolent and inactive.
Stubborn fat is metabolized particularly slowly and resists the hormonal process that takes place when the fat burning process starts up. To burn fat, the adrenal hormones (better known as adrenaline and noradrenaline) attach to the fat cell receptors and basically “open them up” so the fat can be used in the energy pathways. There are two kinds of receptors in the fat cells: alpha and beta. The beta receptors are much more vigorous and respond to adrenal hormones. To lose body fat, the adrenal hormones switch on and the body begins to use fat as energy. Nevertheless, in the case of people with stubborn fat, this does not occur, so no body fat is lost.
Ori Hofmekler in his book The Warrior Diet states that stubborn fat has a lower ratio of beta receptors to alpha receptors. As a result, the body’s hormonal fat dissolver, adrenaline, is unable to enter the fat cell and open the door. The author also points out that “to make these matters worse, stubborn fat has more estrogen receptors, which cause even a larger quantity of stubborn fat.” And what makes it even worse is that people indulge in the typical modern diet and sedentary lifestyle and that factor often results in insulin sensitivity.