Most recruits live with their mothers, only 54 per cent of whom are still married.
This is the first time a detailed portrait of Army recruits has ever been released.
The worst problem recruits encounter when they first join the Army is homesickness, said the study. They miss their mothers most of all; girlfriends and boyfriends come second, followed closely by their pets.
Of the 59 per cent who smoke, the average recruit gets through 13 cigarettes a day. The 84 per cent who drink have an average of 11 pints of beer a week. And although they are more interested in sport than others of their age group, they are not far less fit than Army recruits used to be.
The Army announced yesterday that it was extending its basic recruits' training to cope with soldiers whose lifestyle has given them the "worst possible start to Army life".
Last year, the Army hoped to recruit 15,000 young people but managed only 11,000.
The pool from which ranking officers are drawn has been getting smaller and is increasingly focused on a narrow band of youngsters from relatively deprived backgrounds - which may help explain the thuggish behaviour of some soldiers.
Many of the young people who might once have joined the army and risen swiftly through the ranks to become sergeants and warrant officers now go to university instead.
Half of those who join already have a friend in the Army; 12 per cent a brother. But, in general, "peer pressure" discourages people from joining.
Lieutenant Colonel Richard Quicke, commander of the Winchester training regiment, said the problems lie in a "couch potato" culture, where young people wear trainers, shun competitive sports, eat badly and see commitment and loyalty to the workplace as unfashionable.Reuse content