The worst I've ever felt in the past 3 years of starting my new eating habits is when I had to go back to my old one of eating a carb-heavy diet (didn't have much in terms of choices or options). Ended up heavily constipated and feeling like I needed to slam back energy drinks just to keep myself going back 6pm. Once I finally got home and back on my usual grind of a low-card diet, all those issues cleared up instantly.

Also, since we're talking about large food companies influencing studies, I want to remind people that the push towards exercise as an efficacious method of weight loss for the average person is funded by Coca Cola.