A study from Czechoslovakia showed that obesity is inherited. Czechoslovakia has a registry of twins who are separated from each other at birth and given to foster parents.
Many years later, researchers located the twins and found that they were equally likely to be obese and have the same resting metabolic rate, which is a measure of how many calories they burn while they are doing nothing. Obesity in the twins had little to do with whether the foster parents were obese or skinny, what the parents and children ate, or how much they exercised. Since obesity appears to be inherited, doctors must look for a genetic cause. So far, we know that the stomachs of obese people produce too little ghrelin, one of the hormones that control hunger. Obesity will eventually be cured by a specific medical treatment, not by fad diets. My weight loss recommendations
A twin study of weight loss and metabolic efficiency. V Hainer, A Stunkard, M Kunesova, J Parizkova, V Stich, DB Allison. International Journal of Obesity, 2001, Vol 25, Iss 4, pp 533-537. Hainer V, Charles Univ, Gen Fac Hosp, Obes Management Ctr, Lannova 2, Prague 11000 1, CZECH REPUBLIC