I believe it from personal experience. In the past 40 years I had at least half a dozen extended periods of low carb dieting. Every time I managed to stick with the diet consistently I ended up exercising and I enjoyed the exercise. When I returned to eating SAD the exercise routine always came to an end even though I tried to keep it going. In 2013 I was an undiagnosed T2 diabetic. I remember feeling unbelievably wiped out all the time. I rarely got out of my chair. When I did start testing my BG I found it was high all the time and through the roof when I ate anything with some carbs. In 2014 I started eating low carb as a lifestyle. Within weeks of starting the diet I again felt compelled to get up and move even though I weighed over 400 pounds and had chronic lower back pain. So not only can you not 'outrun a bad diet' if you have issues with high blood sugar the last thing that you want to do is exercise. It does seem counterintuitive that with so much glucose running through the veins why wouldn't our muscles be bursting with energy to use it? I've known people that get hyper when they've eating too much sugar. I've always just wanted to take a nap after a SAD meal. I guess some peoples carburetors get flooded and some don't. It is very possible that how high your BG goes after a meal could be the reason for the difference in behavior.