Physiology of Eating and Exercise

So today I want to talk briefly about food and exercise, focusing mostly on why you should eat immediately after exercise. In fact, I prefer to exercise first thing in the morning, so that I don’t have a chance to get hungry and make my exercise more difficult. I’ll also briefly mention a few things you should know about your diet, which can help you make educated choices about eating and your workout. Let’s get started, shall we?

So let’s talk about what happens when you eat and when you exercise. When you eat, blood flow is concentrated into your vital organs, especially your stomach and intestines (and of course other organs like liver and pancreas to name a few). This blood is used for various purposes depending on the location – the stomach lining secretes acid, and your various organs synthesize their respective digestive fluids and enzymes. This process of rerouting the blood actually begins around the time you see or smell your food (especially smell, it’s what causes you to salivate, which is the first step), and persists for at least an hour after you eat, depending on the volume of the meal. The larger the meal, the more blood that is rerouted. This is part of why you feel lethargic after a large meal – not only has blood been flowing away from your muscles while certain hormones tell your body to lie still so digestion can progress. Exercise on the other hand, reroutes your blood from these organs and puts it into your muscles, so they can be effectively contracted and loosened. So what happens if both of these processes happen at once, for example if you eat then immediately go for a swim or run, or simply don’t put enough time between the two. It creates a conflict in the body, where certain processes are trying to put blood in one place, while others are trying to take it away. And in the end only one process wins. If the digestive processes win, you’ll suffer from cramping due to lactic acid buildup and side stitches. If the muscular processes win, you’ll likely throw up – your body is averse to leaving non-digesting food within itself (it’s ideal conditions for bacterial growth and if it didn’t you would get very sick very easily). But what if you exercise immediately before you eat? Well, exercise will increase your metabolism, and your muscles will needs salts and protein to replenish themselves. This means that a greater part of what you eat immediately after exercise will be used, compared to if you had eaten after sitting around. So try to eat after you run!

Now I want to talk about a few dietary decisions, most notably potentially cutting out dairy products and orange juice (or timing their consumption). Most importantly, you should have neither of these until after a workout – orange juice raises acidity in the stomach which can cause vomiting in an intense workout, and dairy products have several adverse effects. First is that they leave a thin film down your throat and in your stomach, which can interfere with proper breathing, especially when swimming. They contain lactose which is used to create lactic acid – the chemical which causes muscular soreness. Finally, acidity in the stomach can cause curdling especially in intense exercise, which almost certainly leads to nausea. For orange juice, I mostly recommend timing its consumption – only drink water before exercise, and make sure to have lots of it. As for dairy, you might want to consider cutting it out, especially if you are strength training. I’ve found that when I do workouts that leave me sore, I can alleviate some of the soreness by eliminating dairy. But if you typically don’t get sore, eliminating dairy won’t really have any effect on soreness. So toss that around, and try it out – you might find it helps you a lot!

Hopefully now you’re a little more informed on why you should time your workouts and meals. Happy exercising!