Research has shown that a lack of sleep can lead to weight gain. Changes in sleep cycles can affect eating patterns and mood, causing people to overeat.

Some people gain weight initially when they stop smoking tobacco products. Experts believe that this occurs both because nicotine suppresses appetite and because withdrawal symptoms may include stress, which can lead to overeating.

People with polycystic ovary syndrome (PCOS) may find that they gain weight easily around their middle. PCOS causes the ovaries to produce abnormally high levels of male sex hormones.

Rapid weight gain or swelling in particular areas of the body can be due to fluid retention and may be a sign of heart failure.

Sudden weight gain or swelling in the body could be a symptom of kidney disease, such as kidney failure or nephrotic syndrome, which is damage to the kidneys.

If people experience rapid weight gain and their abdomen looks enlarged, this may indicate cirrhosis. Cirrhosis is a condition in which scar tissue replaces healthy tissue in the liver, and it can cause fluid to build up in the abdominal cavity.

A thyroid disorder called hypothyroidism can slow down the metabolism, which can result in weight gain.

Cushing’s syndrome occurs when the body produces too much cortisol over a prolonged period. Cortisol is a hormone that enables the body to respond to stress.

Acromegaly is a hormonal condition that happens when the pituitary gland produces too much growth hormone. It most commonly presents in middle adulthood.

Certain medications can cause people to gain weight rapidly.