Shat's weight was at it's most problematic during the end of the 2nd season. In The Ultimate Computer, director Lucas avoids the full side-shots like the plague: in the teaser where he meets Bob Wesley, they bring him around the transporter console to hide the belly. In Omega Glory, there is that unfortunate shot of him and his chins lying unconscious after being bonked on the head by Cloud William.
In "Inside Star Trek" by Justman and Solow, there's a memo where Justman calls attention to Shatners weight, how people at the (March 68) Emmys were noticing he looked "heavy".
Filming on the 3rd season began in late May 68, and in Spectre of the Gun some of the early shots on the Bridge have Shatner looking tubby, but as the episode progressed, and by the time of Spock's Brain, he had definitely taken off about 10 pounds.
Then he started to slip again, where by Cloud Minders he was looking zaftig again. Then he trimmed a few so he could take his shirt off in Turnabout Intruder, where, faux-abs or not, he looked pretty good.
Hey, when you're 5'8", no matter what you do, you're at a disadvantage when filmed next to the taller and eternally slim DeForest Kelley and Leonard Nimoy. You either starve and end up with the biceps of Kelley or workout 2-3 hours a day, not easy when you've got a 12-hour shooting schedule 6 days a week.
