excess fat is stored in the body deep in side the body (viscera) or superficial (subcutaneous). It may be distributed in two forms. Central or Android (apple shape) or Gynoid (pear shape) obesity. Central obesity (apple shape) is when fat is deposited on the abdomen, trunk and neck. This form of obesity is common in men. Abdominal girth is much bigger in central or Android obesity. It is also true that abdominal (central) obesity is worse than the gynoid (pear shape) obesity because it exports insulin resistance, leading to metabolic syndrome, type 2 diabetes, high blood pressure, fatty liver disease, hyperlipidemia, sleep apnea and others. The Gynoid (pear shape) obesity is when fat is distributed in the hip and thigh area. This type of obesity (Gynoid) is more common in women though some men will have it as well. The gynoid obesity is not as strong as the Android obesity in causing obesity related morbidities such as insulin resistance (metabolic syndrome) as the abdominal girth is not increased to the degree of the Android obesity.
The majority of obesity whether it is Android or Gynoid are caused by lack of regular physical activity, wrong diet and excess calorie ingestion. Few cases of obesity are as a result of hormonal imbalances and genetic abnormalities. Some of the hormone causes of over weight can be thyroid hormone deficiency, excess cortisol, insulin resistance, leptin abnormalities etcetera. Obesity (overweight) due to hormonal imbalances will follow the Android or central obesity form of body fat distribution. In cortisol excess for example, the fat distribution is more prominent on the trunk and neck. There are also rare genetic abnormalities that can cause obesity. These are beyond the scope of our discussion at this time.
The human history has been so successful that we have evolved into a complex and affluent modern society. From the days of scarcity ( hunter and Gatherer) we have evolved into a wealthy society with plenty of food and endless festivities. during the days of food scarcity in the era of hunter and gatherer society a thrifty gene evolved for our survival. The thrifty gene helped as gain more weight during plenty (hunting season) and we used the body fat to survive during scarcity when there was little prey to hunt. The thrifty gene was able to store more fat by creating insulin resistance during the seasons of plenty. Those calories were used during the time of scarcity. The thrifty gene was therefore a survival gene in that era. The people who had the thrifty gene faired better than the people with out the thrifty gene. AS we became affluent the thrifty gene was no longer needed, and instead it be became a liability. It continued to unleash the epidemics of obesity leading to the metabolic syndrome mostly through insulin resistance.
Suppose we all go to the Kalahari desert to become hunter and gatherers or we go to some poor countries where there is food scarcity, regardless of the thrifty gene our body fat will melt in a matter of time. It is therefore important to appreciate that wrong diet (high carbohydrate and high saturated fat), excess calorie intake and lack of daily regular exercise are driving most of our obesity and its co-morbidities. It is therefore important to remember that nutrition is the whole mark of the maximum expression of the gene. The more food we have the more maladaptive genes will express leading to more medical problems.
Going back to your question, your son most likely gaining excess due to wrong diet (high carbohydrate, high saturated fat) excess calorie ingestion and lack of daily regular physical activity like the majority of over weight and obese people in the USA, though there could be a slim possibility of hormonal imbalance. It is therefore very important that you see your son's doctor for proper evaluation. You should ask him to run some tests to rule out hormonal imbalances and check for any genetic conditions. If his weight gain is due to hormone problems, things will improve with correcting the hormone imbalance.
The most important issue is to recognize that wrong diet, excess calorie intake and lack of regular (daily) physical activity are the overwhelming causes of the overweight/obesity epidemics in the USA. So I encourage you to look in to this issue. Healthy balanced diet with bigger portions of vegetables and regular daily structured physical activity should be intensified to maintain an ideal body weight. You should see a good nutritionist to give you a nutritional guide. Provide your son with healthy diet, limit calorie intake with out restricting growth and daily structured physical activity. Create partnership with a good nutritionist and your doctor and you as the leader of the team. If he still continues to gain more weight despite all endeavors, ask your doctor for appetite suppressing medications.
Discuss these issues with you doctor and listen to his expert advice and work as a team.
Other conditions can be associated with an underactive pituitary system where the TSH itself is insufficient, therefore, the thyroid gland is under-stimulated. Can occur (rarely) alone or more often in association with other hypothalamic or pituitary insufficiencies from tumors, cysts, radiation to the region, surgery to the region, trauma to the region. If other hormones (ACTH, GH, TSH, LH, FSH as well as problems with posterior pituitary causing diabetes insipidus as well as abnormalities of MSh and Prolactin) are involved, then growth hormone can also be deficient or insufficient.
Growth hormone deficiency is also associated with weight excess. In kids still growing, then height gain will be too slow associated with weight gain. Specific testing can be done with blood work, bone age X-rays and MRI of pituitary region to help sort this out. If GH deficiency is diagnosed, GH is available to correct the situation and the associated weight excess
usually goes away.
Adrenal cortisol hormone excess (Cushing's) also associated with significant weight gain/obesity also with decreased height. Can be a problem of the adrenal glands themselves or from getting too much cortisone, prednisone or dexamethasone used usually for anti-inflammatory treatment of a variety of illnesses. If not from medication, then blood hormone levels of cortisol and pituitary ACTH can help make a diagnosis. Also will need ultrasound or MRI of adrenal regions themselves as well as pituitary accordingly. Treatment once diagnosis is made, is specific for source of the problem that explains the excess and could be medication, surgery, etc.
So, the answer to the question is a bit complicated. Good history and physical exam and review of plotted wight and height data on charts most often allows consideration of possible diagnostic possibilities and consideration for referral to an endocrinologist for consultation and treatment.
Stuart Brink, MD