Should You Eat Before Exercise with PMOS? The Insulin Resistance Question

This post is part of my complete guide to fuelling PMOS workouts.

"Should I eat before I exercise? I have insulin resistance, so I don't really want to spike my blood sugar."

This is probably the question I'm asked most often whenever I talk about fuelling exercise.

It makes complete sense why so many women with PMOS worry about eating carbohydrates before a workout. We spend so much time talking about balancing blood sugar, choosing higher-fibre carbohydrates and reducing added sugars that it's easy to assume eating before exercise must somehow work against everything we're trying to achieve.

Thankfully, that's not what the research shows.

Why exercise changes the rules

One of the remarkable things about exercise is that it changes the way your muscles use glucose. At rest, glucose largely enters your muscle cells with the help of insulin. During exercise, however, your muscles have another way of taking up glucose. Muscle contractions stimulate specialised transporters called GLUT-4, allowing glucose to move from your bloodstream into your muscles with much less reliance on insulin. In simple terms, exercise helps your muscles become much more efficient at using the carbohydrate you've eaten (Richter & Hargreaves, 2013).

That effect doesn't stop when your workout finishes. For many hours afterwards, your muscles remain more sensitive to insulin as they work to replenish the glycogen stores you've used during exercise. This is one of the reasons regular physical activity plays such an important role in improving insulin sensitivity over time (Bird & Hawley, 2017).

Rather than undoing the benefits of exercise, eating some carbohydrate afterwards is actually supporting one of the recovery processes your body is naturally trying to achieve.

"But won't I just eat back the calories I've burned?"

It's a completely understandable question, particularly if you've spent years following diets that encouraged you to create the biggest calorie deficit possible. Many of us have been taught to think of exercise as a way to "earn" food or burn off what we've eaten, so replacing some of that energy afterwards can feel counterintuitive.

The reality is a little more nuanced than that.

When you finish a workout, your body isn't keeping score of calories. It knows you've asked it to do something physically demanding and now it needs the raw materials to recover. Your muscles have used glycogen, tiny amounts of muscle damage have occurred (which is exactly what we want after strength training), and your body is now working hard to repair those muscles, replenish its energy stores and adapt so that it's fitter and stronger the next time you exercise.

That recovery process requires energy.

It's also important to remember that fat loss isn't determined by one snack before or after a workout. Research consistently shows that eating around exercise doesn't prevent fat loss when your overall energy intake is appropriate. In fact, fuelling properly often allows you to train harder, recover better, maintain muscle mass and stay more consistent with exercise over the long term, all of which support better health and body composition (Thomas et al., 2016; Kerksick et al., 2017).

This doesn't mean carbohydrate quality suddenly becomes irrelevant. Most of the time, I still encourage women with PMOS to build meals around higher-fibre, minimally processed carbohydrates because they're beneficial for blood sugar management, gut health and overall health. Around exercise, however, your priorities shift slightly. Your body is trying to perform, recover and replenish its energy stores, so this isn't the time to worry about whether a carbohydrate is "perfect".

Sometimes the best pre-workout snack really is a banana. Sometimes it's two slices of toast. Sometimes it's a glass of chocolate milk after football training. Those foods aren't "good" or "bad". They're simply doing a job.

Rather than asking yourself, "Will this spike my blood sugar?", I'd encourage you to ask a slightly different question: "What does my body need from me to get the most out of this workout?" I think you'll often find the answer is very different.

"What if I'm trying to improve my insulin resistance?"

This is where many women with PMOS feel caught between two pieces of advice.

On the one hand, you've been told that exercise is one of the best ways to improve insulin sensitivity. On the other, you've been told to be careful with carbohydrates. It can feel like those messages contradict each other.

They don't.

Regular exercise and a balanced diet rich in fibre, protein and minimally processed foods remain some of the most effective lifestyle strategies for improving insulin sensitivity. Eating some carbohydrate around your workouts doesn't undo those benefits. Quite the opposite - your muscles are primed to use glucose during and after exercise, making this one of the most appropriate times to include carbohydrate in your day.

The goal has never been to avoid carbohydrate completely. The goal is to use it well.

If insulin resistance is at the centre of how you're feeling around exercise and food, that's exactly what we untangle together in an Initial Assessment and Roadmap.

Book your Initial Assessment and Roadmap here.

Next: What to Eat Before a Workout with PMOS → COMING SOON

References:

Bird, S.R. and Hawley, J.A. (2017) Update on the effects of physical activity on insulin sensitivity in humans. BMJ Open Sport & Exercise Medicine, 2(1), e000143. https://doi.org/10.1136/bmjsem-2016-000143

Kerksick, C.M., Arent, S., Schoenfeld, B.J., Stout, J.R., Campbell, B., Wilborn, C.D., Taylor, L., Kalman, D., Smith-Ryan, A.E., Kreider, R.B., Willoughby, D., Arciero, P.J., VanDusseldorp, T.A., Ormsbee, M.J., Wildman, R., Greenwood, M., Ziegenfuss, T.N., Aragon, A.A. and Antonio, J. (2017) International Society of Sports Nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition, 14, 33. https://doi.org/10.1186/s12970-017-0189-4

Richter, E.A. and Hargreaves, M. (2013) Exercise, GLUT4, and skeletal muscle glucose uptake. Physiological Reviews, 93(3), 993–1017. https://doi.org/10.1152/physrev.00038.2012

Thomas, D.T., Erdman, K.A. and Burke, L.M. (2016) American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Medicine and Science in Sports and Exercise, 48(3), 543–568. https://doi.org/10.1249/MSS.0000000000000852