Why Fasted Training Is Overrated for 99% of Athletes
Fasted runs are trendy, but the science says most athletes are better off fueled. Here's why training with food in your stomach beats exercising on empty.
Quick Answer
Fasted training offers minimal metabolic advantages for most athletes while reducing performance, increasing injury risk, and compromising recovery — fuel your training for better results.
It sounds appealing: wake up, skip breakfast, go for a run. Burn more fat. Train like a caveman. Get leaner, faster.
Fast forward a few weeks: you're tired, your paces are slow, you're getting injured, and your race times aren't improving.
Here's the truth: fasted training is overrated for 99% of athletes.
Where the Fasted Training Myth Comes From
The idea has some science behind it:
- When you exercise without eating, you use more fat for fuel
- Elite athletes in the 1970s allegedly trained fasted
- Some fat adaptation protocols use fasted sessions
- The theory: train your body to burn fat, spare glycogen for race day
The problem? Most of this research doesn't translate to real-world endurance performance.
What the Science Actually Says
Recent meta-analyses and real-world studies reveal a different picture:
| Feature | Measure | Fasted Training | Fueled Training |
|---|---|---|---|
| Performance (VO2, time trial) | 5–15% lower | Higher | |
| Training quality | Reduced intensity | Better adherence | |
| Injury risk | Higher (low energy) | Lower | |
| Recovery speed | Slower | Faster | |
| Fat loss (long-term) | Minimal difference | Same or better |
Bottom line: fasted training might increase fat oxidation during the session, but it doesn't lead to better body composition or race performance.
Why Fasted Training Fails Most Athletes
1. You Can't Train as Hard
Without carbs in your system, you simply don't have the same energy available. Your paces slow, your intervals suffer, and you're not training at the intensity that drives adaptation.
2. Glycogen Depletion Compounds
Every fasted session depletes glycogen stores. Over a training block, this adds up:
- Recovery between sessions takes longer
- You're more likely to bonk in later workouts
- Muscle protein breakdown increases
- Immune function drops
3. Injury Risk Increases
Low energy availability (eating less than you burn) is one of the biggest risk factors for stress fractures and overuse injuries. Fasted training often leads to chronic underfueling.
4. Fat Adaptation Takes Forever
The proposed benefit of fat adaptation — using more fat so you spare glycogen for race day — requires:
- Weeks of strict low-carb dieting
- Multiple fasted sessions per week
- Ongoing maintenance protocols
- No guarantee of race-day benefit
Most athletes would be better served by simply practicing race-day nutrition.
When Fasted Training Might Work
There are narrow use cases:
- Easy, short recovery runs where intensity doesn't matter
- Athletes with specific metabolic adaptations (rare)
- Experienced athletes who've tried everything else
Even in these cases, the benefits are marginal at best.
What to Do Instead
If you want better performance and body composition:
- Fuel around training: eat before and during workouts
- Do hard sessions fueled, easy sessions easy (but still fed)
- Focus on total daily energy intake, not meal timing tricks
- Practice race-day nutrition in training sessions
- Sleep more, stress less — these move the needle more than fasting
The Better Approach: Training Fed
Here's a simple framework:
| Feature | Session Type | Fueling Strategy |
|---|---|---|
| Easy recovery runs | Small snack or light breakfast, optional | |
| Long runs | Full pre-run meal, fuel during (30–90 g/hr) | |
| Intervals / Tempo | Pre-run meal, possible intra-run fueling | |
| Race simulations | Full race-day fueling protocol |
The goal: train at the intensity prescribed by your plan. You can't do that if you're running on empty.
Fuel your training properly.
Download MAVRFrequently Asked Questions (FAQ)
What about fasted cardio for fat loss?
Total daily calorie deficit matters more than meal timing. You'll lose the same fat eating before or after exercise.
Can I ever do fasted training?
Short, easy recovery runs are the safest option. But even then, a small snack usually improves quality.
What about the athletes who swear by it?
Confirmation bias is strong. They might perform better for other reasons (training consistency, sleep, nutrition overall).
Does MAVR recommend fasted training?
No. MAVR provides fueling recommendations that support training quality and recovery.