Intermittent Fasting for Athletes: Does It Improve Performance or Fat Loss?
In this episode of the Find Your Edge podcast, Coach Chris Newport sits down with Dr. Matthew Stratton, who recently completed his doctoral research on intermittent fasting and resistance training performance. Together they break down what intermittent fasting really is, what the science says, and whether it offers any advantages for athletes.
What Is Intermittent Fasting?
Intermittent fasting (IF) is not a single diet—it is a broad category of eating patterns that alternate between periods of fasting and feeding.
The key rule: no caloric intake during the fasting window. Non-caloric beverages like water, black coffee, or diet soda are typically allowed during a “wet fast.”
Common Intermittent Fasting Protocols
- Time Restricted Eating (TRE): The most popular method, often using a 16-hour fast and 8-hour eating window.
- Alternate Day Fasting: Eating normally one day and fasting the next.
- Modified Alternate Day Fasting: Eating normally one day and consuming only 300–500 calories the next.
- Periodic Fasting: Longer fasts performed occasionally, such as a 24-hour fast once per week.
Most people who practice intermittent fasting are following the 16:8 time-restricted eating model, often eating between noon and 8 PM.
Why Intermittent Fasting Became So Popular
Intermittent fasting gained attention partly because it simplifies dieting. Instead of focusing on what to eat, it focuses on when to eat.
Research shows that many people naturally reduce their calorie intake by about 20% when following fasting protocols, largely because they have less time available to eat.
The “Dirty Secret” of Intermittent Fasting
According to Dr. Stratton, the biggest reason intermittent fasting works for weight loss is simple:
Most people unintentionally eat fewer calories.
By shortening the eating window, people often feel fuller during meals but still end up consuming fewer calories overall.
The Research Question: Does Fasting Improve Performance?
Much of the early intermittent fasting research did not control for calorie intake. This made it difficult to determine whether improvements were caused by fasting itself or simply by reduced calories.
Dr. Stratton’s research addressed this problem by controlling food intake across groups.
Key Study Design
- 32 trained men
- 4-week supervised resistance training program
- All participants consumed the same calories (~1900/day)
- Protein intake controlled (~1.8 g/kg body weight)
- Body composition measured with a research gold-standard 4-compartment model
The goal was to determine whether intermittent fasting itself influenced body composition or performance when calories were identical.
Study Results: No Advantage When Calories Are Equal
The results were straightforward.
When calorie intake and protein intake were controlled:
- No difference in strength gains
- No difference in muscle growth
- No difference in fat loss
- No difference in resting metabolic rate
In other words, intermittent fasting did not provide a performance or fat-loss advantage beyond calorie control.
Does Skipping Breakfast Hurt Afternoon Workouts?
Dr. Stratton’s dissertation research also examined a common question: does skipping breakfast reduce performance later in the day?
Participants either ate breakfast or skipped it but consumed identical total calories later in the day before resistance training.
The result: no meaningful difference in training performance.
The Psychological Component of Performance
Interestingly, some earlier research showed performance drops when athletes skipped breakfast. However, when researchers used placebo meals, those differences often disappeared.
This suggests that expectations—believing you need breakfast to perform—can influence results.
What About Fasted Training?
Training while fasted can increase perceived effort.
Many athletes report a higher rating of perceived exertion (RPE) when exercising without eating. This can lead to self-selected lower intensity workouts.
Research suggests fasted training affects performance more significantly when:
- Workouts exceed one hour
- Intensity is high
- Carbohydrate stores are low
For this reason, most studies recommend placing workouts inside the feeding window whenever possible.
Should Athletes Use Intermittent Fasting?
The biggest takeaway from the research:
Intermittent fasting is an option—but not a magic solution.
If it fits your lifestyle and helps you maintain a calorie deficit, it can be effective for weight loss. But it does not appear to offer additional metabolic or performance advantages.
Practical Takeaways for Athletes
- Choose an eating pattern you can stick with long term.
- Focus on total calorie intake first.
- Prioritize adequate protein intake.
- Ensure endurance athletes get enough carbohydrates.
- Whenever possible, place workouts inside the feeding window.
Final Thoughts
As Dr. Stratton summarized best:
“You do you.”
If intermittent fasting works for your lifestyle, it can be successful. If it doesn’t, there are many other evidence-based approaches to nutrition that work just as well.
