The only place you can see weight gains is by looking at Table I and working it out yourself for each subject, and only the last subject PW had an outlying weig

The only place you can see weight gains is by looking at Table I and working it out yourself for each subject, and only the last subject PW had an outlying weight gain in absolute terms but his starting weight was also an outlier - his relative gain was the same as all the others as well. The paper is about how the weight of fat cells changed at different subject weights, not how much subject weight changed for a fixed food size - the only mention of food portions is with respect to ensuring weight was maintained, gained and lost for the different stages. "After desired or maximum obtainable weight was reached" indicates they weren't using weight as the outcome here. The only place you can see the weight gains is by looking at Table I and working it out yourself for each subject, and the relative gains are all very similar: 23.3%, 25.3%, 21.4%, 20.0% and 18.0%. I'm guessing they wanted them to put on 20-25% of their body weight to give consistent and measurable changes to the fat cells.