Best-selling author, David Pink, released a new book that’s getting plenty of buzz. When: The Scientific Secrets of Perfect Timing is a guide to timing everything from when to exercise to when to schedule surgery to optimize results based on scientific studies. I can’t speak to the best time to schedule surgery, but the book’s recommendations regarding exercise are in my wheel house and I’ve a few things to say about them.
This post isn’t about refuting the science nor the advice Pink gives. Though I haven’t read his book, the summaries I’ve read indicate Pink takes sound, peer reviewed exercise studies and synthesizes the results into straight-forward advice on when to exercise for the best results according to a person’s goals. Rather, I’m asking whether the recommendations are practical, or even viable, for the average person in real life situations. And I’m using personal experience to back up my assertions.
The Advice: If your goal is weight loss, you should exercise first thing in the morning, before breakfast.
The Science: Studies have shown a person will burn more stored body fat as fuel for exercise if she exercises before breakfast compared to exercising after breakfast.
The Logic: During exercise, the body burns stored carbohydrates in muscle (glycogen) as fuel first and, only after glycogen stores have been depleted, will the body burn stored body fat as fuel. In the morning, one’s glycogen stores are at their lowest due to the overnight fast the body has endured. Therefore, if an individual wishes to maximize body fat burn during exercise for weight loss, one should exercise before breakfast.
Makes sense, right? I knew about the studies that proved this phenomenon before Thanksgiving this past year. I normally workout mid to late morning because that’s what works best with my schedule and it feels right to me. But, I thought Thanksgiving morning would be the perfect time to try this out. I never felt so ill after a workout in my life.
What happened? Two things. First, low glycogen stores also means, for many, less than optimal blood sugar (glucose). It wouldn’t take much exercise for glucose to drop too low to properly fuel continued exercise under those circumstances. Light-headedness, irritability, headache and nausea are common symptoms of low blood sugar. The other, more debilitating phenomenon was I was dehydrated. As the logic above suggests, the overnight fast not only depletes glycogen stores but also water.
I was aware of this that morning and drank water (and avoided caffeine) before my workout, but not nearly enough. However, if I had drunk more water prior to my workout, I would’ve had to wait longer to exercise to avoid stomach cramping. This, in turn, would have further delayed my breakfast, compounding the effects of low blood sugar during exercise. All of this to say that, while the science and logic pass muster, the advice isn’t practical for many and, for some, may be impossible to follow.
I realized a few things that day. Number one, I can’t workout before breakfast. Number two, my body is inclined to naturally use this logic on its own. My sweet spot for workouts is between 11am and noon. My workouts are most productive and challenging and my post-workout high most satisfying when they’re in that timeframe.
I feel slightly hungry at 11am as I’ve digested breakfast, yet I’ve had enough time to normalize my hydration levels. Which means, while my glycogen stores aren’t as low as they were when I woke up, they are depleted to a degree by 11:00 and, if my workout is long enough or vigorous enough, I will use them up and begin to burn fat for fuel near the end of my workout as well as during post-workout calorie burn (known as EPOC) without becoming dehydrated. My body has been using the science to my advantage in the way that worked best for me.
That’s what we all should do. Just because a study tells us we should do this or avoid that doesn’t mean that we have to, or even can, follow the advice exactly as it’s given. Sometimes we have to recognize our limitations and unique circumstances and figure out how we can manipulate the concept behind the advice to fit our lifestyles.
If optimizing fat burn is your exercise goal but working out before breakfast isn’t practical or possible, here are a few ways to hack the recommendation:
- Have a small, high-carb snack and 16-24 oz of water as soon as you get up and perform your workout 30-60 minutes after eating. Follow the workout with a calorically moderate, high-protein breakfast, such as: eggs and toast; oatmeal (made with milk) with nuts/seeds; plain kefir, nut butter & banana smoothie
- Perform your workout several hours after your last meal and about an hour before the next meal (lunch or dinner). Be sure you’re hydrating regularly throughout the day as opposed to trying to hydrate all at once before the workout.
- Make the workouts count – structure them so you deplete your glycogen stores and ensure some body fat for fuel. Here are three examples. Pick one that best suits your abilities, workout preferences and schedule:
- 30-40 min traditional interval workouts or <30 min HIIT workouts
- Moderate intensity cardio (walking, cycling, swimming) for 60+ mins
- Full-body strength training workout followed immediately by moderate intensity cardio: 40-60 min total
One of my most common refrains as a trainer to people who’ve had difficulty adopting an exercise routine is to ignore all the advice telling us about the best – the best gym, the best workout, the best time to exercise. The best is relative. If working out before breakfast doesn’t work for you then it can’t possibly be your best time to workout. The best workout is one that you will do because you enjoy it and it fits your lifestyle. Hack the science to meet your needs, not the other way around.