So far the increase in size has gone along with increases in longevity, but I wonder if that can continue.
To take just a few examples, the average adult man in 1850 in America stood about 5 feet 7 inches and weighed about 146 pounds; someone born then was expected to live until about 45. In the 1980s the typical man in his early 30s was about 5 feet 10 inches tall, weighed about 174 pounds and was likely to pass his 75th birthday.
Across the Atlantic, at the time of the French Revolution, a 30-something Frenchman weighed about 110 pounds, compared with 170 pounds now. And in Norway an average 22-year-old man was about 5 ½ inches taller at the end of the 20th century (5 feet 10.7 inches) than in the middle of the 18th century (5 feet 5.2 inches).