England prop Mako Vunipola revealed how head coach Eddie Jones advised him to lose some weight ahead of four home Tests later this year.
Jones' men will face South Africa, Fiji, Argentina and Australia at Twickenham across November and December as they bid to continue their excellent progress under Jones.
Since the early exit under Stuart Lancaster at the Rugby World Cup last year, England have won all nine Tests with Jones in charge, including a Six Nations Grand Slam and a 3-0 whitewash of the Wallabies Down Under.
Vunipola was included in Jones' 37-man training squad for those Tests, with the final party set to be announced later this month, and the Saracens prop has been told to watch his food intake.
"A couple of weeks ago I got a letter saying I was in contention. Everyone got a letter, reminding us what to work on," he told reporters.
"Mine said not to eat too much - to lose some weight.
"I tried to look after what I ate and my diet during the summer. Eddie keeps you on your toes.
"I'm fighting for my place in this squad. Joe Marler's a world-class player so to have him back in the squad is a bonus."