I added a "sprint" day last week and was really happy with how good it felt to break a sweat in such a short time. I read of a new definition of "sprinting" on my favorite health blog. He said in addition to real sprints, you can consider as a sprint any complex movement you can do with good form for a few reps. Like say you can do four push ups with good form. Do 5-10 sets of four, with 45 seconds to 1 minute break in between each set.
So I did a pushup / burpee sprint routine and ended up doing nine sets! I was sweaty, exhilarated, and I didn't have to go outside on a chilly, rainy day.
Raisin, I have been off sugar and simple carbs permanently now for three years, and it is one of the best things I have ever done for myself. You probably already know this but it takes 3 weeks for your body to get over the "low carb flu" which is the detox. Headache, stupidity, nausea, no energy. Then one day, you wake up and you feel ... so GREAT! It's totally worth it.