This has long been one that has divided the fitness/nutrition world. On one hand there are lots of fitness professionals that spout the benefits of fasted cardio (working out before you have eaten anything first thing in the morning - generally you won't have eaten for about 10 - 12 hours overnight). This has been shown to help rev up your metabolism and to get your body into the "fat burning" zone. While others say that you perform at your best after having eaten a small snack beforehand as that then gives you the energy to perform better.
There have been many studies in relation to this and they have shown that fasted cardio does allow you to burn slightly more fat as it can activate certain fat burning genes - HOWEVER - and this is a big however they have mostly been done on obese males. So yes, if you are an obese male fasted cardio may slightly help you to burn more fat.
More recent findings however have shown that weight and fat loss from exercise is more likely to be enhanced through dietary changes. Things like reducing the amount of alcohol you intake, skipping the dessert and halving the amount of rice or pasta that you eat are going to help and do the same for your weight loss efforts as doing fasted cardio does.
That is not to say that you shouldn't do fasted cardio. If you feel good doing it and feel you can perform at your optimal then go for it. Just like if it takes you a while to get up and going in the morning then exercising later in the day when you have more energy is going to be more beneficial to you.
Things to think about to decide whether to do fasted cardio
1. Your Everyday life - What is your daily routine and life like. if you start work at 6 or 7am then chances are that you are not going to have time to do fasted cardio in the morning before going to work and that your workouts will generally be later in the afternoon or night.
2. Your preference for when you like to workout - if you have a 9am - 5pm job and have the choice to exercise in the morning or afternoon then it's up to your preference as when you want to do it. As I say, exercise should be something that you enjoy, not a chore. So if you aren't a morning person and find that you perform your best at night, then forcing yourself to do fasted cardio in the morning will make you not perform at your best and you won't get much out of your sessions. If you do exercise in the morning, chances are you aren't going to want to get up and eat straight away before you go to the gym so they are more likely to be fasted sessions. Just like if you are training at night, it is harder to do fasted cardio as you will generally have eaten within the last few hours.
3. Doing a workout anytime is better than not doing a workout - This is the most important of them all. Fasted or not fasted, getting out and moving your body and exercising is going to be a lot more beneficial to your overall health, energy levels and vitality and weight loss efforts than not doing it. So just because you think you may not be burning as much fat because you are exercising after eating a light meal or snack, don't let that stop you.
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