ORCHARD PARK, N.Y. -- Buffalo Bills running back Karlos Williams showed up out of shape to mandatory minicamp Tuesday and later claimed his poor conditioning was because of his fiancée's recent pregnancy and her associated food cravings.

"I like to eat and then her being pregnant gave me an excuse to eat, so eating anything and everything," Williams said. "She'd wake up, one or two o'clock, 'I want a snack.' Well I'm not going to sit here and watch you eat because I don't want you to feel bad, but it's back to football. She's getting back to working out herself, so kind of motivating each other, feed off each other's energy, and we're getting ready for camp."

Williams, 23, welcomed his fourth child last month. When asked Tuesday if he was dealing with an injury, Williams responded, "The injury of pregnancy, I would say."

Williams, who is listed on the Bills' roster at 230 pounds, appeared heftier than that weight at Tuesday's practice after missing organized team activities this spring. Williams participated in warm-up drills before assistant strength and conditioning coach Eric Ciano put the second-year bruiser to work on an exercise bike on the sideline.

"I don't think it's gonna be easy. I don't think that at all," coach Rex Ryan said Tuesday when asked about getting Williams back in shape. "Obviously, he's had some different things. I know some personal things, all that. But we do have to be slow with him."

Ryan said the Bills won't put "a ridiculous weight number" on Williams for when he returns to training camp next month.

"We're gonna put something that's attainable for him," Ryan said. "But what you don't want to do, you don't want to have him -- all the sudden he's gonna drop 20 pounds and he comes out here and he gets hurt the first day of training camp. That's what we're trying to avoid.

"So we got to get him to the right things. Obviously he's not anywhere close to where he needs to be to play at a high level. We got to get some weight off of him and he certainly understands that."

Williams, a 2015 fifth-round pick from Florida State, averaged 5.6 yards on 93 carries last season, sixth-most among NFL running backs with at least 30 carries. He averaged 2.27 yards after contact per carry, ninth-most among the same group of backs. He missed a total of five games because of a concussion and, later, a shoulder injury.

Ryan is disappointed about Williams' conditioning after his promising rookie campaign.

"Sure, absolutely," Ryan said Tuesday. "But, he knows. Obviously, you wish that he was in much better shape. There's no question about it. I think in the future, he's gotta realize that what he did this offseason is far from what you want. But he's a young guy. Hopefully he'll learn from it."