How Your Body Uses Macros for Fuel

Dieting is crucial when it comes to working out. It doesn't just apply to seeing results such as weight loss or muscle gain. What you eat beforehand plays a major role in your performance for that gym session. In this blog post, I will explain how your body burns nutrients during a workout.

Macros in Fitness

Of the three macros, fats and carbs are the most useful DURING a workout, and proteins are most useful AFTER a workout. The reason for this is that fats and carbs are easily converted into ATP, our body's primary source of energy, whereas proteins are most useful in healing our bodies after a workout. Fats are mostly used for low-intensity, aerobic (with oxygen) workouts, and carbs are mostly used for high intensity, anaerobic (without oxygen) workouts. 

Ventilatory Thresholds

Your body burns calories throughout the day through a process called basal metabolic rate (BMR), and these calories are contributed to bodily functions such as breathing and blood circulation. This is where you'll burn most of your daily calories, however if you're looking to increase the number of calories burned per day, exercise is crucial. The number of calories you burn during exercise depends on the intensity of your workout, and that is where ventilatory thresholds (VT) come into play. 

Below VT1

This stage includes relatively relaxed workouts such as walking or light jogging. Below VT1, breathing is relatively easy, and you can talk comfortably. At this stage, you are mostly burning fats.

Between VT1 and VT2 

At this stage, you are burning about 50% fats and 50% carbs. Within this threshold, you are performing at a higher intensity. For aerobic workouts, this might consist of sprints, and for weightlifting workouts this may consist of supersets. 

It's worth noting that this is probably the "sweet spot" for losing weight. It may sound ideal to burn more fats than carbs, but think of it this way: in 20 minutes of exercise below VT1, you may have burned 20 fats, but in 20 minutes above VT1, you may have burned 15 fats and 15 carbs, equaling 30 total nutrients burned. Excess carbs are converted into fats anyways, so this may be the ideal threshold. 

Above VT2

At this stage, you are using almost exclusively carbs. This is for powerful, explosive movements such as a one rep max or a timed sprint. This is why you'll hear sprinters talking about eating a bowl of pasta before a big race - carbs are very important for explosive performance!

Conclusion

Understanding how your body uses macros for fuel is crucial for not only weight loss, but also for your performance in the gym. Hopefully this helped you understand what you should consume depending on your goals!

Disclaimers

By no means am I a certified nutrition coach. All of the information presented was obtained via the National Association of Sports and Medicine's Certified Personal Trainer program.