Well I exercise 3 times to 4 times a day and have no problems and strenuous workouts i might say! Never had headaches but I don't eat red meat now I cut out meat all together except fish...I love SOUTHBEACH and if you stick to the program it really works. No loss of energy for me but then it depends on what your diet was like before. As for breakfast during phase 1 I ate tuna and walnuts or cheese anything i felt like within PHASE I eat your dinner for breakfast if you like there is no set way to eat only the foods in that particular phase. I personally love SOUTHBEACH it is not a diet but a healthy way of living and Ive tried everything not ATKINS because I was never really a meat eater only chicken so all the best to you!