The 30-year-old is reaping the rewards of the club's twice-daily pre-season training sessions and believes that the intensive schedule will leave the squad in prime condition for the 2013-14 campaign.
"For the first third of last season we caught a lot of people off guard because of how fit we were," he told the club's official website
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"This is probably the leanest I’ve been in my whole career. I’m feeling good and I’m feeling strong.
"I haven’t struggled in training so far and I’m looking forward to seeing what pre-season brings. I can’t wait for the start of the new season."
Foster is also excited about the arrival of experienced French striker Nicolas Anelka, who completed a move to the Baggies last week.
"Nicolas seems a really lovely lad," he added. "He’s going to be a fantastic addition to the squad.
"We’re all looking forward to seeing him in action. I really want to see his butterfly celebration too. I always remember seeing him do that when he scored goals at Chelsea. I want to see him do it plenty of times this season!"