Consequently, it is likely that Lambert's weight gain was caused not by a physical disorder but by a combination of overeating and a lack of exercise. Although heavily built in his teens, he began to gain weight only when he took up the relatively sedentary job of prison keeper. A biography of Lambert published during his lifetime recounted that "it was within a year of this appointment that his bulk received the greatest and most rapid encrease". Although he claimed to eat little, and to abstain from alcohol, it is likely that a man with his lifestyle and position in society would have eaten large amounts of meat, and drunk beer at social events.