For more than 40 years I weighed the same 170 pounds. I wasn’t trying to lose weight, yet a simple 12-hour eating window — nothing between 6pm and 6am — subtly changed my metabolism, my performance, and my understanding of longevity. Here’s the surprising science behind it.
It’s Not What You Eat, It’s When You Eat: The Case for Time-Restricted Eating
For most of my adult life, my weight was a constant. No matter how much I trained, raced, or refined my nutrition, the scale always hovered around 170 pounds — the same weight I was in high school. It became such a fixed part of my identity that I stopped thinking it would ever change.
So when I started time-restricted eating (TRE), I wasn’t trying to manipulate my weight at all. I did it purely to experiment with hormesis benefits — the cellular “training effect” that mild stressors provide for long-term health and longevity. My only rule was simple:
No calories between 6pm and 6am.
Everything else stayed exactly the same.
What happened surprised me.
The Unexpected Trend
Because I weigh myself daily on a digital scale, I have a good sense of patterns. At first, nothing seemed different. But after about three months, the trend line definitely showed a pattern — I was losing 1–2 pounds per month, month after month, for about 9 months, eventually settling around 155 pounds.
I didn’t change what I ate. I didn’t change how I trained. I didn’t feel hungrier.
And yet, I was feeling lighter and climbing faster on my bike.
This period overlaps with my structured training improvements (detailed here: How structured training transformed my performance at 60), but the weight loss itself was purely a function of when I ate — not the volume or content of my meals.
Metabolic Health: What My Bloodwork Shows
My labs during this period also support improved metabolic stability:
- Glucose: 89 mg/dL
- Insulin: 3 µIU/mL
- HbA1c: 5.8%
- Triglycerides: 53 mg/dL
- hsCRP: 0.2 mg/L
All of these fall into ranges associated with improved metabolic flexibility, low inflammation, and favorable cardiovascular risk profiles. None of this occurred through calorie counting or dieting — just consistency in giving my body a nightly break from food.
Why Timing Matters: The Science of TRE
1. Your Metabolism Runs on a Clock
Dr. Satchin Panda at the Salk Institute helped popularize the idea that nearly every organ — liver, pancreas, gut, fat tissue, even skeletal muscle — operates on a circadian rhythm. These clocks anticipate feeding and fasting cycles.
Eating late at night, when these metabolic clocks are winding down, leads to:
- Higher insulin responses
- Less efficient glucose handling
- More fat storage
- Reduced overnight repair processes
A consistent eating window helps synchronize these clocks and improves metabolic efficiency.
2. Fasting Activates AMPK and Reduces mTOR — the “Longevity Switches”
Research from Valter Longo, David Sinclair, and others has shown that periods without meals activate pathways linked to longevity:
- AMPK, a sensor of cellular energy scarcity, ramps up fat burning and mitochondrial efficiency.
- mTOR, a growth-promoting pathway, quiets down — allowing cells to enter repair mode.
- Autophagy, the recycling of damaged cellular components, increases after extended nightly fasting.
You can think of this as giving your cells time to take out the trash.
3. Insulin and Metabolic Flexibility Improve
Studies by Courtney Peterson and Ruth Patterson have shown that TRE can:
- Lower fasting insulin
- Improve insulin sensitivity
- Reduce evening glucose excursions
- Decrease nighttime hunger hormones
Interestingly, many of these benefits occur even when no change in calorie intake is made — which matches my own experience.
4. Fat Oxidation Increases Overnight
With 12 hours of fasting every night, your body has a long, predictable window without incoming calories. Studies show this enhances:
- Lipolysis (fat breakdown)
- Mitochondrial efficiency
- Overnight fatty-acid utilization
Steady, low-level fat loss over months aligns with these mechanisms.
Hormesis: Why a Little Stress Makes You Stronger
TRE belongs to a bigger family of longevity tools based on hormesis — the concept that mild stressors trigger adaptive, beneficial responses.
Examples include:
- Exercise — microtears stimulate stronger muscle; mitochondrial stress improves endurance.
- Cold exposure — increases norepinephrine and brown fat activation.
- Heat exposure — boosts heat-shock proteins and cardiovascular conditioning.
- Fasting / caloric restriction — activates cellular repair, enhances metabolic flexibility, improves longevity in multiple species.
Work from Michael Ristow, Andrzej Bartke, Gustavo Barja, and others consistently shows that these mild, repeated stressors increase healthspan — the number of years lived in good health.
I didn’t try water fasts, multi-day fasts, or severe caloric restriction. My only lever was timing — but even that low-friction intervention taps the same biological machinery.
It Wasn’t Hard… Except Socially
Most people assume fasting requires willpower or leaves you hungry. That wasn’t the case for me.
The challenge was entirely social:
- Late dinners
- Evening events
- Social drinking (yes, alcohol counts as calories)
TRE was easy physiologically but occasionally tricky culturally.
Why This Matters for Aging Well
The most surprising part of this experience wasn’t the weight loss — it was the realization that my metabolism wasn’t a constant. After 40+ years at the same weight, my body composition shifted simply by respecting my internal rhythms.
Pairing TRE with structured training improved:
- Power
- Strength
- Endurance
- Climbing speed
- Recovery markers
- Bloodwork stability
The long-term benefits? Hard to quantify yet, but I’m optimistic. TRE feels like one of those rare interventions that is:
- Simple
- Inexpensive
- Evidence-backed
- Sustainable
- Compatible with performance training
And if the longevity science is right, it might be doing quiet work underneath — conditioning cells, stabilizing metabolism, and nudging the trajectory of aging in the right direction.
I’m excited to continue the experiment.
The Old New Mexican 
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