When you are under stress, the adrenal glands release cortisol, and this increases blood-sugar levels, so you have the energy to respond to stressful situations. So far, so good; this response is healthy in the short term.
However, when the causes of stress are continuous, elevated cortisol levels can create higher insulin resistance, and this can lead to type 2 diabetes. Aside from increasing the risk of diabetes, insulin resistance can make you feel hungry, and of course, that may result in overeating and weight gain.
The elevated cortisol levels that occur in the first phase of adrenal fatigue also can slow down the hypothalamus and pituitary gland. In turn, this affects thyroid function and metabolism, causing you to feel constantly tired. To counter this, a typical response is to overload on high-sugar foods and carbs, again causing weight problems.
Also, high cortisol and blood-sugar levels encourage fat storage in the abdomen. Various studies link elevated cortisol levels to increases in visceral fat (aka belly fat), even in people who are otherwise slim.
Just as too much cortisol can cause exhaustion, so can too little. During the final phases of adrenal fatigue, the adrenals no longer produce sufficient cortisol to fire the body up under stress, and blood-sugar levels drop. Extreme tiredness kicks in, and the vicious cycle of unhealthy eating or caffeine consumption continues.