Personally, I have struggled with my weight my whole adult life. I do get that a lot of us exercise to help lose and control our weight. Do I think that we can exercise to lose weight and be competitive in a competition while eating nutritiously for both? The simple answer is, No. The body cannot do both weight loss and strength/endurance building at the same time. I am not saying that you cannot set a goal to lose weight and run the local 5k, but if you are training to win the 5k then feed your body for competition.
There are very few of us who are good at multitasking. I know I am not a good multitasker. My mind is just not made to do a variety of things at one time. It is the same way for the body of most of us. Our bodies are good at doing one task at a time. A good example is eating and exercise. The suggested time for a meal before running is 2 to 4 hours prior to hitting the pavement. It takes the stomach roughly 4 hours to empty after eating a full meal. For snacks and fluids it can take 1 to 2 hours less. When we go out for a run our bodies have to switch from the task of digestion to exercise. This means that all of the effort the body was putting forth for digestion now has to change course and support exercise. Our heart has to work to pump blood to our working muscles and lungs to support running. While this is happening blood has moved from the task of wholly supporting digestion to support energy production. There are other body processes that have to pause or slow down to support the activity of running.
Now, back to why I think eating for weight loss and being competitive is not feasible for most of us. The body is getting two separate signals if we try both at the same time. When we eat to lose weight we are taking in fewer calories per day so we can support weight loss. At the same time we need to eat to maintain our performance goals for competition. The body is getting mixed signals here. What will most likely happen if we try to maintain both tasks? The body will have to start cannibalizing muscle to support the energy needs we are demanding that it make for competitive training. At some point we will start seeing our training efforts start to decline because we are not supporting the demands of training with the needed nutrition.
So go ahead and eat to lose weight. Run that 5k next weekend and have a good time. When you think you want to run a race and get a new PR it is time to change nutrition goals to feed the body for competition.