How to Fuel High Intensity Interval Training

I was recently interviewed by Sara Curry of Blaze Yoga and Pilates to talk about why her students are bonking during Inferno Hot Pilates -- a type of heated pilates that incorporates High Intensity Interval Training, or HIIT.

Bonking, crashing, hitting the it what you want, but when it happens, it sucks.

The great thing about HIIT is that you get a killer transformative effective workout in a short period of time...but ONLY if you’re adequately fed. Here are some common mistakes people make when trying to fuel their high intensity interval training.

Top 4 Reasons You’re Bonking During a Workout

1. You’re undereating.

If you’re not eating enough food or calories, this will cause you to crash during your workout.

If you’re purposely undereating for weight loss purposes, I encourage you to reframe your mindset from weight LOSS to muscle BUILD.

When we think about losing fat, we immediately go into restriction mode. But when we under-eat calories, this can become a metabolic disaster. Instead, if you focusing on building lean muscle mass, it’s going to get you the results you’re after -- including increased metabolic rate (read: burning more calories while at rest), longevity and vitality.

When we focus on BUILDING, this puts in more of a position to understand that we must fuel adequately.

2. You’re fasting.

This goes hand-in-hand with undereating (duh), but since intermittent fasting AND fasted workouts are very en vogue right now, it’s worth mentioning.

Fasting DOES have its merits and utility, but NOT for everyone. In fact, I think fasting (intermittent or otherwise) is contraindicated for the following groups:

  • Anyone with a history of eating disorders or restrictive eating patterns

  • Anyone with low blood sugar

  • Anyone who has adrenal fatigue/HPA axis dysregulation or  is under a lot of life stress

So that covers just about ALL of my female clients.

Fasting is a stressor -- it raises stress hormones in the body -- and the last thing we want to do when under stress is add MORE stress.

Now keep in mind not all stress is bad -- in fact, we need external stressors in our life in order to adapt, grow stronger and more resilient. But if you’re already under stress, then additional stress shouldn’t come from diet.

Instead, you can try heat therapy. Get into a sauna or a hot yoga class.

3. You’ve got low blood sugar.

When blood sugar gets too low (also known as hypogylcemia), both your brain and body run out of their preferred fuel source.

Low blood sugar is WAY more common than we think. In fact, I see it so frequently in my practice that I developed an entire nutrition program dedicated to blood sugar regulation. Dysregulated blood sugar can be at the crux of SO MANY health issues and symptoms, so it’s absolute ground zero for reclaiming your energy and health.

Other signs of low blood sugar:

  • Irritability if meals are missed (watch my video on HANGER here)

  • Needing to eat to relieve fatigue

  • Dependency on coffee and sugar for energy

  • Feeling light headed, spacey, shaky or jittery

  • Feeling agitated and nervous

  • Become upset easily

  • Poor memory, forgetfulness

  • Blurred vision

3 big reasons for low blood sugar:

  1. Underereating

  2. Skipping meals

  3. Relying on a high carbohydrate diet (this spikes blood sugar and then you deal with a subsequent crashing leading to low blood sugar symptoms -- including bonking during workouts)

High intensity interval training increases glucose demands, so if you’re already starting with low blood sugar, it can make you feel a lot worse.

But that’s actually really GREAT news if you have high blood sugar.

A note on high blood sugar:

Chronic high blood sugar can lead to insulin resistance, metabolic syndrome and diabetes, an epidemic in the modern world.

HIIT activates something called the AMPK pathway. This is the central pathway for managing blood sugar issues, insulin and a healthy metabolism -- it also determines whether we burn fat or store fat.

The more intense the exercise, the faster you clear insulin and glucose from the blood -- and the longer the effects last. If you know you have high blood sugar, it might make sense to include more HIIT into your training.

4. You’re Not Eating Enough Carbs

A ketogenic diet is one that produces ketones -- ketones can serve as an alternative fuel source for your brain and body. BUT the fast twitch muscle fibers that we’re using in HIIT cannot get energy from ketones. This means that if you’re on a keto or low carb diet, you may not have adequate fuel in your gas tank for a HIIT workout.

High intensity training doesn’t usually pair well with a very low carbohydrate or ketogenic diet.

I learned this the hard way.

I eat a moderately low carbohydrate to manage health conditions, and it works really well for me. But when I started increasing the intensity and frequency of my workouts, it felt like a one way ticket to Bonk City. I just didn’t have the energy to get through IHP class like I wanted to.

Here’s the deal: carbohydrate intake exists on a spectrum. On the one end, we have the Standard American Diet bringing in roughly 300 grams of carbs per day. To the other end, we’ve got the keto diet with under 30 grams of carbs per day. We act like these two extremes are our only option. They’re not.

Carb intake isn’t as black and white as “low carb vs. high carb”. There are MANY shades of grey in between. Carb tolerance is high individualized based on your unique physiology and certain external variables (for example, interval training can actually increase carb tolerance).

Figuring out YOUR unique carbohydrate needs is a way to unlock your energy and health. This is exactly what we do in the Carb Compatibility Project™.

If you want to remain on a low carb diet but also still practice HIIT for its health benefits, then consider a more targeted carbohydrate approach -- you’ll learn exactly how to do this on the CCP!

Signs that you’re not properly fueling your workout_ “Bonking” during workout Reliance on caffeine or a “pre-workout” supplement before working out Feeling dizzy or seeing stars during a workout Feeling weak or fatig.png

So what SHOULD you eat to fuel your HIIT workouts?

Well, it depends.

The tricky part about nutrition as a science is that we’re all so biochemically different. Pre and post workout nutrition is very person-specific. Nothing works exactly the same for 2 people.

Some folks just need to swap out a highly processed food diet for a more whole foods diet.

Some need to stop skipping meals.

Some people are already doing these things and could benefit from playing around with macros & meal timing (if this is you, join in on the Carb Compatibility Project™!)

Read this blog for more specific ways to fuel your workout.

If the research is indicating that we have to go hard to get the most benefits from our exercise, then I want to go hard and get the most bang for my buck. If I can modulate that through food, that feels like a huge win.

If you’re ready to invest some time to tinker around and figure out what you need to eat to show up to your workout like a badass, then jump in on the next round of the Carb Compatibility Project™!