Personally, I use IF to help control my bodyweight and fat %. But lots of clients and athletes often ask me how on earth you can do this and still train... Well, it's all about working out what works for you and your body around your training plan.
For example, the 5:2 principle doesn't work well for me as I can't train hard on the off days. However, a 14-16hr daily fast does... I'll try to do my cardio work when fasted and then do any HIIT or S&C sessions later in the day when I'm fuelled. Where for some people, who have a very busy work schedule, the 5:2 principle is thrown in on busy day's where training just isn't possible and it works well.
It can work great for all types of clients and athletes, however, you need to get it right for you.
Have a read of this article by Training Peaks and if you'd like to discuss how to make it work for you then just get in touch.
Increase Fat Oxidation Exercising in the fasted state forces the body to use its energy systems more efficiently, since carbohydrate stores are nearly depleted after a 12-16 hour fast. Fasting also activates the body’s sympathetic nervous system (SNS) which is responsible for our fight-or-flight response. When the SNS is activated, heart rate increases, digestion slows, and muscle tension increases. During fasted exercise, the activation of the SNS causes an increased breakdown of fat for energy (Varady et al. 2013). Fat oxidation also increases for 24 hours following a fasted workout (i.e. an easy aerobic exercise session done first-thing in the morning following an 8-12 hour overnight fast). Essentially, fasting helps your body become better at metabolizing fat rather than relying on the carbohydrates that are readily available in a non-fasted state.