As a keen cyclist, I’m always looking for an edge. Whether I’m grinding up a steep climb on my road bike or navigating a muddy trail on my mountain bike, I want to be at my best. That’s why I decided to try intermittent fasting (IF). For a while now, I’ve been following an 18:6 fasting schedule during the weekdays – that’s 18 hours of fasting with a 6-hour window to eat. On weekends, I relax the rules and eat more freely, especially with the longer rides I tend to do.

But a question has been nagging at me: is this approach actually helping my performance, or could I be doing more harm than good? I decided to do a deep dive into the science and answer three key questions for myself, and for any other “Muckers” out there who might be curious.

My 3 Big Questions:

1. Is my weekday 18:6 fasting routine beneficial or detrimental to my cycling?
2. When I do eat, what kind of food should I be focusing on to maximize my performance?
3. Is a ketogenic (low-carb) diet a good option for a cyclist like me?

Here’s what I found out.

Question 1: Is My 18:6 Fasting Doing More Harm Than Good?

This was my biggest concern. Am I shooting myself in the foot by restricting my eating times, especially with the amount of training I do? After digging into the research, the answer is a resounding: it’s likely doing more good than harm, but with a few very important caveats.

Here’s a breakdown of the pros and cons I discovered:

The Good Stuff (The Pros):

• Improved Power-to-Weight Ratio: This is a big one for us cyclists. Intermittent fasting has been shown to be an effective tool for fat loss while preserving muscle mass (if you do it right!). The result? A better power-to-weight ratio, which means you’re hauling less weight up those hills for the same power output.
• Becoming a Fat-Burning Machine: When you fast, your body gets better at using its fat stores for energy, especially during lower-intensity rides. This is great for building endurance and can help you avoid the dreaded “bonk” on long rides.
• Weekend Refeeds are a Secret Weapon: My weekend “off” from fasting isn’t a lack of discipline; it’s a strategic advantage! I now see my weekends as a crucial “refeeding” period. After a week of fasting and training, this is my chance to fully restock my glycogen (carbohydrate) stores, which is essential for fueling those big weekend rides. It also gives my metabolism a boost and keeps me from feeling deprived.

The Potential Pitfalls (The Cons) & How to Fix Them:

• High-Intensity Performance Can Suffer: This is the most critical takeaway. Trying to smash a high-intensity interval session or a steep, punchy climb deep into a fast is a recipe for disaster. Your body needs readily available carbohydrates for these all-out efforts.
  • The Fix: I now schedule my toughest workouts during my eating window, ideally 2-3 hours after a meal containing carbs. I save my fasted rides for low-intensity, steady-state sessions (what coaches call Zone 1-2).
• The Risk of Muscle Loss: While IF can help preserve muscle, there’s a risk of losing it if you’re not careful, especially when you’re in a calorie deficit to lose weight.
  • The Fix: Two things are non-negotiable here: eating enough protein (we’ll get to that in a bit) and incorporating some resistance training into my week. Lifting weights or doing bodyweight exercises sends a signal to my body to hold on to its muscle.

The Verdict: My weekday fasting routine gets a thumbs up, mainly because of the weekend flexibility. It’s a smart way to manage my weight and improve my fat metabolism without sacrificing my weekend warrior status.

Question 2: What Should I Eat in My 6-Hour Window?

This brings me to my second question. If I only have a six-hour window to eat, what I put on my plate becomes incredibly important. The key here is nutrient density. Every calorie has to count. This isn’t a license to eat whatever I want for six hours (a “dirty fast”). To get the real benefits, I need to fuel my body with high-quality foods.

Here’s my nutritional game plan now:

1. Protein: The Recovery Cornerstone

Protein is crucial for repairing and rebuilding the muscle I break down during my rides. This is especially important when I’m fasting.

• How much? The science points to a target of 1.6 to 2.2 grams of protein per kilogram of body weight. For example, a 75kg (165lbs) person would aim for 120-165g of protein per day.
• What kind? I’m focusing on lean protein sources like chicken, turkey, fish (especially salmon for its anti-inflammatory omega-3s), eggs, and Greek yogurt.

2. Carbohydrates: The High-Performance Fuel

Carbs are not the enemy! For a cyclist, they are the high-octane fuel we need for performance. The trick is to eat the right kind at the right time.

• How much? This depends on my training load. On rest days, I’ll eat fewer carbs. On days with long or intense rides, I’ll eat more. A good range for cyclists is 3 to 8 grams of carbs per kilogram of body weight.
• What kind? I’m loading up on complex carbs that provide sustained energy. Think sweet potatoes, quinoa, brown rice, oats, and lots of fruits and vegetables. I save simple sugars (like gels and sports drinks) for during and immediately after hard rides.

3. Healthy Fats: The Foundation for Health

Healthy fats are essential for hormone production, reducing inflammation, and keeping me feeling full during my fasting periods.

• How much? After I’ve hit my protein and carb targets, the rest of my calories come from healthy fats.
• What kind? I’m getting my fats from avocados, nuts, seeds, and olive oil.

A Sample Day of Eating:

Here’s how I might structure my eating on a training day with an evening ride (eating window from 1:00 PM to 7:00 PM):

• 1:00 PM (Lunch): A large salad with grilled chicken, avocado, quinoa, and plenty of veggies.
• 4:00 PM (Pre-Ride Snack): A bowl of Greek yogurt with berries or a bowl of oatmeal with a banana.
• 6:00 PM – 7:00 PM (Ride): I’ll have a sports drink on hand for a hard session.
• Immediately Post-Ride (and before 7:00 PM): A recovery smoothie with whey protein and a banana, followed by a small dinner of salmon, sweet potato, and broccoli.

Question 3: Is a Keto Diet a Good Idea for Me?

With all the buzz around keto, I had to ask: would a low-carb, high-fat diet be a good fit for my cycling? The answer, after looking at the evidence, is a clear and resounding no.

Here’s why a ketogenic diet is not a good choice for a serious cyclist who wants to perform at their best:

• You Lose Your Top Gear: High-intensity efforts – the very things that win races and make you a stronger rider (sprints, attacks, steep climbs) – rely on your body’s ability to quickly burn carbohydrates. A keto diet shuts down this energy system. Even after you’re “keto-adapted,” you lose that top-end power and speed. It’s like taking the turbo out of your engine.
• Performance is Compromised: Research consistently shows that while keto can be great for low-intensity endurance, it significantly impairs high-intensity performance. For the dynamic, varied demands of road and mountain biking, this is a huge disadvantage.
• My Current System is Better: My current approach of weekday fasting with a balanced diet and weekend carb refeeds is far superior to a cyclical ketogenic diet. I get the fat-burning benefits without sacrificing the high-intensity performance that makes cycling so much fun.

The Mucker’s Takeaway: My Action Plan

My deep dive into the science has been a real eye-opener. I feel more confident than ever in my approach, but with a few key refinements. Here’s my action plan going forward, which might be helpful for you too:

• Prioritize Protein: I’m making sure I hit my daily protein goals to protect my muscles.
• Align My Training and Nutrition: My hardest rides are now on the weekends when I’m fully fueled. Fasted rides are strictly for easy recovery sessions.
• Focus on Whole Foods: My 6-hour eating window is a chance to nourish my body with the best possible foods.
• Forget Keto: I’m sticking to a balanced diet with plenty of carbs to fuel my performance.
• Stay Hydrated: I’m drinking plenty of water, black coffee, and herbal tea, especially during my fasts.
• Embrace Strength Training: I’m committed to hitting the weights twice a week to combat age-related muscle loss and build a more resilient body.

A Note for My Fellow Mature Muckers (40+)

The science also shows that our bodies change as we get older, and we need to adapt our strategies.

• For the 40+ Women: Female hormones can be more sensitive to fasting. A less aggressive approach like a 14:10 fast (14 hours of fasting, 10-hour eating window) or fasting only on 2-3 days a week might be a better fit. The most important thing is to listen to your body. Also, prioritize calcium, vitamin D, and weight-bearing exercise for bone health.
• For the 50+ Men: The risk of age-related muscle loss (sarcopenia) is real. So, hitting that high-protein target and consistently doing resistance training is non-negotiable.

Listen Up, Muckers!

Don’t have time to read? No problem. You can listen to an audio version of this post on Spotify https://open.spotify.com/episode/0Qy90MHBQaAgpz6QtuY90v?si=gGhnZ9DQQHG0bvL-JZCRDw

Ride on!