Time-Restricted Fasting Plus NMN Boosts Endurance in Mice
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New research reveals synergistic effects on mitochondrial function and gut health, but human translation remains uncertain
A recent study published in Nutrients (2025) has revealed intriguing findings about combining time-restricted fasting with NMN supplementation. Researchers observed significant improvements in endurance, strength, and coordination in mice, alongside enhanced mitochondrial function and beneficial shifts in gut bacteria.
Whilst these results are promising, it's important to understand what this means for human application and what questions remain unanswered.
"This study suggests that timing matters as much as what you supplement. The synergy between fasting and NMN makes biological sense - fasting activates pathways that demand NAD+, whilst NMN provides the substrate. What's particularly interesting is the gut microbiome shift, suggesting NAD+ support works through mechanisms we're still uncovering. However, mouse studies don't translate directly to humans. For those already practising time-restricted eating and taking NMN, this provides theoretical support for potential synergies worth exploring carefully."
— Mat Stuckey, Founder of Longevity Formulas
What the Study Found
The research tested whether adding NMN (Nicotinamide Mononucleotide), a direct precursor to NAD+, could amplify the benefits of time-restricted fasting. After six weeks, mice receiving both interventions showed:
- Longer running time before exhaustion
- Increased grip strength
- Better motor coordination
- Reduced oxidative damage following exercise
- Enhanced mitochondrial function
- Beneficial changes in gut bacteria composition
- Increased production of short-chain fatty acids (SCFAs)
These findings suggest a synergistic effect between fasting and NAD+ support, though the mechanisms in humans remain to be established.
Study Design and Methods
The research involved 65 male mice divided into five groups:
- Control group: Standard ad libitum (unrestricted) feeding
- Time-restricted fasting alone: Food access limited to specific hours
- TF + Low-dose NMN: 125 mg/kg daily
- TF + Medium-dose NMN: 250 mg/kg daily
- TF + High-dose NMN: 500 mg/kg daily
Mice received NMN via daily gavage (direct stomach administration) for six weeks. Researchers then assessed:
- Physical performance: Treadmill running to exhaustion, grip strength tests, rotarod coordination tests
- Metabolic markers: Blood gas analysis, oxidative stress indicators
- Cellular function: Muscle mitochondrial respiration, biogenesis markers, OXPHOS gene expression
- Gut health: Microbiome composition analysis, short-chain fatty acid measurements
Key Results: Performance Improvements
Endurance Enhancement
Mice receiving time-restricted fasting plus NMN demonstrated significantly longer running times before exhaustion compared to either control or fasting-alone groups. This improvement correlated with enhanced mitochondrial function in skeletal muscle, suggesting better cellular energy production.
The endurance boost wasn't simply about having more energy available - it appeared to involve fundamental changes in how muscle cells produced and utilised energy during sustained exercise.
Strength and Coordination Gains
Grip strength testing revealed improvements in the TF+NMN groups, indicating enhanced neuromuscular function. Additionally, rotarod coordination tests showed better motor control, suggesting benefits beyond pure muscle strength.
These findings are particularly interesting because they suggest NMN's effects aren't limited to endurance capacity. The improvements in strength and coordination hint at broader neuromuscular benefits.
Reduced Oxidative Damage
Post-exercise measurements showed lower markers of oxidative stress in the TF+NMN groups. This suggests better antioxidant capacity or reduced free radical production during intense activity, a potential mechanism for improved recovery and reduced exercise-induced damage.
Mechanisms: What Changed at the Cellular Level
Mitochondrial Function Enhancement
The study revealed several mitochondrial improvements:
Increased respiration capacity: Mitochondria in muscle tissue showed enhanced oxygen consumption rates, indicating more efficient energy production.
Upregulated biogenesis: Markers of mitochondrial biogenesis (the creation of new mitochondria) increased, suggesting cells were building more of these energy-producing organelles.
Enhanced OXPHOS gene expression: Genes involved in oxidative phosphorylation, the process by which mitochondria produce ATP, showed increased expression. This suggests not just more mitochondria, but mitochondria that function more efficiently.
The combination of fasting and NMN supplementation appeared to trigger a coordinated response, ramping up the cellular machinery responsible for energy production.
Gut Microbiome Shifts
Perhaps the most intriguing finding was the significant change in gut bacteria composition. The TF+NMN groups showed:
Increased diversity: A more diverse microbiome is generally associated with better metabolic health.
Enrichment of beneficial species: Specifically, populations of Ruminococcus, Roseburia, and Akkermansia increased. These bacteria are known producers of short-chain fatty acids (SCFAs).
Higher SCFA production: Measurements confirmed increased levels of these beneficial metabolites, which play important roles in gut health, inflammation regulation, and energy metabolism.
This microbiome shift is significant because it suggests a potential mechanism linking fasting, NMN, and metabolic improvements. SCFAs, particularly butyrate and propionate, serve as signalling molecules that influence everything from gut barrier function to systemic inflammation and insulin sensitivity.
The NAD+ Connection
NMN works by boosting levels of NAD+ (Nicotinamide Adenine Dinucleotide), a coenzyme essential for mitochondrial function. NAD+ declines naturally with age and can be further depleted by metabolic stress.
Time-restricted fasting also influences NAD+ metabolism, partly through activation of sirtuins, NAD+-dependent enzymes involved in cellular stress resistance and longevity pathways. The combination of fasting (which may increase NAD+ demand and sirtuin activity) with NMN supplementation (which provides substrate to meet that demand) could explain the synergistic effects observed.
What This Means for Human Application
The Translation Challenge
This is where we need to exercise caution. Mouse studies provide valuable mechanistic insights but don't directly translate to human protocols for several reasons:
Metabolic differences: Mice have much faster metabolisms than humans. A six-week intervention in mice doesn't equate to six weeks in humans.
Dosing conversion isn't straightforward: The 125-500 mg/kg doses used in mice don't convert linearly to human doses. Mouse-to-human dose conversion typically involves dividing by a factor of 12.3, which would suggest human equivalent doses of roughly 10-40 mg/kg (700-2,800 mg for a 70 kg person). However, this is highly speculative.
Individual variation: Humans show much more variation in diet, activity levels, baseline fitness, and microbiome composition than laboratory mice.
No human safety data: This specific combination hasn't been tested in controlled human trials.
What We Can Reasonably Hypothesise
Despite these limitations, the study does suggest some plausible hypotheses worth exploring:
Timing matters: The synergy between fasting and NMN suggests that when you take NMN relative to your eating window might influence its effects.
Gut health plays a role: The microbiome changes suggest that NAD+ support might partly work through gut health mechanisms, not just direct cellular effects.
Exercise response could be enhanced: The improvements in both performance and recovery markers suggest potential benefits for training adaptations.
Practical Considerations for Those Experimenting
If you're an endurance athlete, HIIT enthusiast, or longevity-focused individual considering this combination, here are some practical considerations:
Define Your Fasting Window
Time-restricted fasting typically involves limiting food intake to a specific window each day. Common approaches include:
- 16:8: 16 hours fasting, 8-hour eating window
- 14:10: 14 hours fasting, 10-hour eating window
- 18:6: 18 hours fasting, 6-hour eating window
The study doesn't specify the exact fasting protocol used, which is a limitation. Starting with a moderate 14:10 or 16:8 window is sensible for most people.
Consider NMN Timing
Since the mice received NMN daily during fasting periods (via gavage, which bypasses the eating window question), two approaches could be tested:
Morning dosing during fasted state: Taking NMN in the morning before breaking your fast might align with the study protocol.
Pre-exercise dosing: If training fasted, NMN before exercise could potentially support the mitochondrial demands of training.
There's no definitive answer yet. Personal experimentation with consistent tracking would be needed.
Track Concrete Metrics
Rather than relying on subjective feelings, measure objective outcomes:
Performance metrics:
- Time trials or distance covered in fixed time
- Grip strength (easily measured with a hand dynamometer)
- Heart rate recovery after standardised exercise
- Training volume tolerance
Recovery indicators:
- Resting heart rate
- Heart rate variability (HRV)
- Sleep quality metrics
- Perceived recovery scores
Metabolic markers (if accessible):
- Fasting glucose and insulin
- Lactate threshold testing
- VO₂max testing
Gut health indicators:
- Digestive comfort
- Bowel regularity
- Bloating or discomfort
Be Realistic About Timelines
The mouse study ran for six weeks. In human terms, meaningful adaptations to combined interventions likely take 8-12 weeks minimum. Don't expect overnight transformations.
Watch for Warning Signs
Time-restricted fasting isn't appropriate for everyone. Warning signs to stop or modify include:
- Persistent fatigue or declining performance
- Disrupted sleep patterns
- Increased injury susceptibility
- Loss of menstrual cycle regularity (women)
- Obsessive food thoughts or disordered eating patterns
- Social isolation due to eating restrictions
Individual Response Varies
What works for laboratory mice in controlled conditions may not work for you. Factors influencing individual response include:
- Current fitness level
- Training volume and intensity
- Baseline diet quality
- Sleep patterns
- Stress levels
- Existing gut health
- Genetic factors
The Broader Context: Fasting, NAD+, and Longevity
This study fits into a larger body of research exploring how caloric restriction, fasting, and NAD+ metabolism intersect with healthy ageing.
Caloric Restriction and Longevity
Decades of research have shown that caloric restriction (eating fewer calories whilst maintaining adequate nutrition) extends lifespan in multiple species. Time-restricted fasting represents a different approach, focusing on when you eat rather than just how much.
The mechanisms appear to overlap: both interventions influence insulin sensitivity, inflammation, autophagy (cellular cleaning processes), and mitochondrial function. NAD+ metabolism sits at the centre of many of these pathways.
The Mitochondrial Theory of Ageing
One theory of ageing focuses on mitochondrial dysfunction. As we age, mitochondria become less efficient, produce more oxidative stress, and decline in number. This contributes to reduced energy availability, increased inflammation, and cellular damage.
Interventions that support mitochondrial health, whether through fasting, exercise, or NAD+ precursor supplementation, may help slow this decline. The current study adds evidence that combining these approaches might amplify benefits.
The Gut-Muscle Axis
The microbiome findings are particularly relevant to emerging research on the gut-muscle axis. Short-chain fatty acids produced by gut bacteria can influence:
- Muscle protein synthesis
- Mitochondrial biogenesis
- Insulin sensitivity in muscle tissue
- Inflammatory signalling
- Exercise performance and recovery
This suggests that optimising gut health might be an underappreciated component of athletic performance and healthy ageing.
What Further Research Is Needed
To translate these findings to humans, we need:
Human clinical trials: Controlled studies testing time-restricted fasting plus NMN in human subjects, measuring both performance and mechanistic outcomes.
Dose-response studies: What NMN doses produce meaningful effects in humans? Are higher doses better, or is there a plateau or even a U-shaped curve?
Protocol optimisation: What fasting windows work best? Does NMN timing relative to fasting and exercise matter?
Individual variation studies: Can we identify who responds best to this combination? Are there genetic or metabolic markers that predict response?
Long-term safety data: What happens with extended use? Are there any downsides or adaptation effects?
Mechanistic validation: Do the same mitochondrial and microbiome changes occur in humans?
The Bottom Line
This mouse study provides intriguing evidence that combining time-restricted fasting with NMN supplementation may enhance exercise performance, mitochondrial function, and gut health through synergistic mechanisms.
The findings are biologically plausible and align with our understanding of how fasting and NAD+ metabolism influence cellular health. The microbiome component adds an interesting dimension, suggesting effects beyond direct mitochondrial support.
However, this is animal research with no human data yet. The doses, protocols, and effects cannot be directly translated to human use. Anyone considering this combination should:
- Approach it as a personal experiment rather than a proven protocol
- Start conservatively with established time-restricted fasting practices
- Track objective metrics consistently
- Monitor for any negative effects
- Maintain realistic expectations about outcomes and timelines
- Consider consulting with healthcare providers, especially if you have existing health conditions
The study opens interesting questions rather than providing definitive answers. It suggests avenues worth exploring but doesn't constitute evidence that humans should rush to adopt this specific combination.
For those already using NMN for longevity support or practising time-restricted eating, this research provides additional theoretical support for potential synergies. For those new to either intervention, it might be wise to test each independently before combining them.
As always in emerging longevity science, the gap between promising animal research and validated human application remains substantial. Bridging that gap requires patience, rigorous research, and honest acknowledgement of what we know versus what we hope might be true.
Reference: Nutrients 2025, https://doi.org/10.3390/nu17091467
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