This is what I've been thinking. Show me someone who is "struggling to lose weight" and I'll show you someone who has been and still is eating too much and exercising too little. Russert never looked all that healthy to me. Instead of all of the cutting edge medical science he might have gotten more benefit from better food, calorie counting, and more physical activity daily. A lot of that other stuff seems more like treating symptoms than addressing root causes to me.
And yet, if he yo-yo dieted, that would have been worse for him than if he just stayed overweight.