The medico-actuarial height-weight tables of 1912 indicate definitely that the population as a whole gains weight with advancing years. For example, the average weight of a man 5 feet and 10 inches tall, aged 25, is 71.3 kg. (157 lb.), but of a man aged 55 years the weight is 78.6 kg. (173 lb.), a gain of 7.3 kg. (16 lb.). This evidence of actual gain in weight of the population may possibly give a clue to one of the causes of obesity.
What is universally accepted as the basic cause of obesity is an intake of calories in excess of metabolic demands. Obesity may result from an increased intake of calories in the presence of a constant output of energy, from a decreased output in the presence of a constant intake, or from any relative variation of the two. A great deal of attention has been given to the
Pollack H, Consolazio CF, Isaac GJ. METABOLIC DEMANDS AS A FACTOR IN WEIGHT CONTROL. JAMA. 1958;167(2):216-219. doi:10.1001/jama.1958.72990190003016