Android fat distribution describes the distribution of human adipose tissue mainly around the trunk and upper body, in areas such as the abdomen, chest, shoulder and nape of the neck. This pattern may lead to an "apple”-shaped body or central obesity, and is more common in males than in females. Thus, the android fat distribution of men is about 48.6%, which is 10.3% higher than that of premenopausal women. In other cases, an ovoid shape forms, which does not differentiate between men and women. Generally, during early adulthood, females tend to have a more peripheral fat distribution such that their fat is evenly distributed over their body. However, it has been found that as females age, bear children and approach menopause, this distribution shifts towards the android pattern of fat distribution, resulting in a 42.1% increase in android body fat distribution in postmenopausal women. This could potentially provide evolutionary advantages such as lowering a woman's center of gravity making her more stable when carrying offspring.
Android fat distribution is contrasted with gynoid fat distribution, whereby fat around the hips, thighs, and bottom results in a “pear”-shaped body.
Jean Vague, a physician from Marseilles, France, was one of the first individuals to bring to attention the increased risk of developing certain diseases (e.g., diabetes and gout) in individuals with an android distribution compared to a gynoid distribution. There are other health consequences beyond these, including psychological consequences.
Biology
Android fat is readily mobilized by deficits in energy balance. It is stored in different depots to gynoid fat.
Android fat cells are mostly visceral - they are large, deposited deep under the skin and are highly metabolically active. The hormones they secrete have direct access to the liver. The presence of fat in the trunk and upper body in males is facilitated by testosterone. Testosterone circulation causes fat cells to deposit around the abdominal and gluteofemoral region, whereas in women oestrogen circulation leads to fat deposits around areas such as thighs, breasts and buttocks. Therefore, measuring a person's oestrogen to testosterone ratio can reveal their predicted gynoid to android fat distribution. Android fat develops as a back-up source of energy when the male body is experiencing an imbalance, whereas gynoid fat develops after puberty, in order to better prepare the body for supporting a potential infant. 50% of the variance in abdominal fat mass observed in humans is due to genetic factors
The cellular characteristics of adipose tissue in android and [gynoid] obese women are different. Android type have larger fat (hypertrophy) cells whereas gynoid type have increased number of fat cells (hyperplasia). This allows for hypertrophic obesity and hyperplastic obesity. Two different receptors, alpha and beta fat cell receptors, vary in their ability to facilitate or inhibit fat mobilization. Alpha-receptors are predominately in the lower body thus more abundant in gynoid patterns and Beta-receptors are predominantly in the upper body and so more abundant in android patterns.
Causes
Hormonal disorders or fluctuations can lead to the formation of a lot of visceral fat and a protruding abdomen. Medications such as protease inhibitors that are used to treat HIV and AIDS also form visceral fat. Android fat can be controlled with proper diet and exercise. A poor diet with lack of exercise is likely to increase android fat level.
Health consequences
Differences in body fat distribution are found to be associated with high blood pressure, high triglyceride, lower high-density lipoprotein (HDL) cholesterol levels and high fasting and post-oral glucose insulin levels
The android, or male pattern, fat distribution has been associated with a higher incidence of coronary artery disease, in addition to an increase in resistance to insulin in both obese children and adolescents. Studies have also related central abdominal obesity (indicated via increased waist–hip ratio) with increases in peripheral fasting insulin levels.
Android fat is also associated with a change in pressor response in circulation. Specifically, in response to stress in a subject with central obesity the cardiac output dependent pressor response is shifted toward a generalised rise in peripheral resistance with an associated decrease in cardiac output.