I’m a light weight body builder who has always done cardio first thing in the morning on an empty stomach. Did a 1/2 marathon last year and was very successful. Now going back to body building but I want to change my workouts. I would like to strength train 1st thing in the morning and do cardio later in the afternoon. Will I see the same success?
A few things I’d like to add to this great discussion: Under-fueling of any kind eventually leads to the catabolization of lean mass (muscle loss). Whether your current goal is endurance training or a bodybuilding workout, I’ll assume that muscle loss is not a part of your goal, so you may want to reconsider not eating before cardio.
Although you will burn more fat than sugar during a workout by not eating beforehand, you may burn less fat overall. Remember that the highest ratio of fat is usually burned during sleep. Current research is showing that High Intensity Interval Training (HIIT) boosts EPOC (Excess Post-exercise Oxygen Consumption) levels and fat-burning hormones in both men and women for up to 72 hours after a workout. Not eating, on the other hand, will only affect fat burning levels for the amount of time you’re working out. Here’s what the doctor that did the research has to say on the subject: http://www.drlenkravitz.com/Articles/epocarticle.html
The other factor all women should consider when adapting their exercise routine is that engaging in any exercise to the point of amenorrhea, or any disruption of the menstrual cycle, will cause bone density loss, which can in some cases be irretrievable. You can thank me when you’re 80… 😉 http://www.ncbi.nlm.nih.gov/pubmed/16271132