This reminded me of a submission from last week: “Working Out Only on Weekends Is Equal as Daily Exercise” – https://news.ycombinator.com/item?id=32390947
Studies about exercise and weight loss are like the ones about red wine and chocolate. There's a contradictory article every other week.
These sorts of things are accepted or rejected totally based on subjective opinion. If you're a type A person, you're thinking, "This sounds right, I guess I better find a 15 minute slot in my daily schedule." and if you're type B like myself, who shudders at the thought of the monotony of another daily task, you immediately think, "Hey, waitasecond! I thought we could just leave it to the weekend??"
To each their own.
I.e., just exercising on the weekends may be enough to live longer, but spreading weight training out throughout the week is more effective for muscle growth than the equivalent sum of the training on the weekend only.