What 26 Months of Garmin Data Taught Me About Exercise, Weight Loss, and Recovery
I have been wearing a Garmin for a little over two years and wanted to stop guessing. I wanted to know what actually moved my weight, what seemed to improve fitness, and whether I was ever doing enough exercise to hurt recovery instead of help it.
This page is my first pass at that question using my own exported Garmin data: activities, weight, sleep, HRV, VO₂ max, and fitness age.
Key findings
My data says the big lever was not random hard workouts. It was sustained running volume.
About 20 miles per week, or roughly 80 miles across 4 weeks.
Above 80 miles in 4 weeks, weight trend turned favorable.
About 300 minutes per week was where the weight trend started looking better.
I did not find evidence in this dataset that my current exercise level hurt HRV or sleep.
That does not mean every week above 20 miles was magic. Weight is noisy. Travel is noisy. Food is noisy. Stress is noisy. But when I zoomed out to 4-week blocks instead of chasing single-week results, the pattern got much clearer.
About the watch I used
I used a Garmin watch for this whole experiment. If you want to track your own training, sleep, HRV, and fitness trends over time, this is the watch family I used as the backbone for the project.
What was in the dataset
| Activity | Count |
|---|---|
| Treadmill running | 351 |
| Running | 129 |
| Walking | 85 |
| Strength training | 72 |
| Meditation | 30 |
| Cycling | 9 |
This is a running-heavy dataset, so most of the useful conclusions here are really conclusions about running volume, not every possible exercise type.
Question 1: What activities seemed to drive the most weight loss?
For me, the answer was sustained running. I do not have enough clean blocks of walking-only or strength-only training to claim those beat running for weight loss. The data is dominated by treadmill runs and outdoor runs, and the strongest signal followed total run volume more than workout count.
That was one of the more useful takeaways for me personally. It was not about finding the perfect heroic workout. It was about stacking enough miles over enough weeks.
Question 2: Is there a threshold before weight loss begins?
Yes. This was the clearest conclusion in the whole project.
When I looked at 4-week running totals, the break point showed up around 80 miles in 4 weeks. Below that, my average forward weight trend was positive. Above that, it turned negative.
| 4-week run miles bin | Windows | Avg 4-week run miles | Avg forward weight change |
|---|---|---|---|
| 0-40 | 21 | 25.46 | 1.16 |
| 40-60 | 8 | 50.10 | 1.26 |
| 60-80 | 15 | 72.81 | 1.39 |
| 80-100 | 22 | 90.29 | -0.83 |
| 100+ | 17 | 119.48 | -1.11 |
My practical read: if I want the scale to actually move, I probably need to average about 20 miles per week, not just flirt with it once in a while.
The week-to-week view was much noisier, which is exactly how real life feels. A strong week can get erased by travel, restaurant food, poor sleep, or a few off days. The 4-week view felt much more honest.
Question 3: How many minutes of activity seem to matter?
I saw a similar pattern in activity minutes. Once I got to around 1,200 minutes across 4 weeks, or roughly 300 minutes per week, the average weight trend turned favorable.
| 4-week activity minutes bin | Windows | Avg 4-week activity minutes | Avg forward weight change |
|---|---|---|---|
| 0-600 | 9 | 458.27 | 0.85 |
| 600-800 | 8 | 714.54 | 1.71 |
| 800-1000 | 15 | 922.80 | 0.95 |
| 1000-1200 | 14 | 1077.55 | 0.48 |
| 1200+ | 37 | 1475.96 | -0.65 |
That lines up pretty well with the running threshold. It is another way of saying the same thing: enough consistent movement over multiple weeks matters more than random bursts of effort.
Question 4: Did too much exercise seem to hurt HRV or sleep?
This was one of the questions I was most curious about, because I know my HRV gets hit by more than just exercise. What I eat matters. Heat at night matters. Overseas travel absolutely matters. Stress matters too.
Even with that, I still wanted to know whether there was some obvious point where my exercise volume looked counterproductive. In the overlap window available in the export, I did not find that signal.
| Weekly minutes bin | Weeks | Avg weekly minutes | Avg HRV | Avg sleep score |
|---|---|---|---|---|
| 0-120 | 10 | 62.95 | 40.22 | 54.70 |
| 120-180 | 7 | 158.63 | 42.53 | 58.61 |
| 180-240 | 5 | 203.86 | 44.62 | 56.14 |
| 240-300 | 3 | 251.38 | 43.96 | 61.10 |
| 300+ | 3 | 441.81 | 47.57 | 67.76 |
My read: in this dataset, more exercise was neutral to positive for recovery, not negative. That does not mean overtraining is impossible. It means I did not find evidence that I reached it here.
Question 5: How many rest days per week should I have?
This was the weakest signal in the project.
| Rest days bin | Weeks | Avg rest days | Avg next-week weight change |
|---|---|---|---|
| 0 | 23 | 0.00 | -0.39 |
| 1 | 23 | 1.00 | 0.20 |
| 2 | 14 | 2.00 | 0.44 |
| 3+ | 27 | 3.85 | -0.32 |
My honest conclusion is that this dataset does not support a strong universal rule like “two rest days is always best.” Real life muddies it too much. Travel weeks, illness weeks, stressful weeks, and broken-routine weeks all create extra rest days for reasons that have nothing to do with a smart training plan.
What did seem stronger was this: rest-day count mattered less than whether I maintained enough total volume across the month.
Question 6: How much exercise is actually counterproductive?
At least in this export, I cannot find a clean upper limit where training clearly started hurting me. The highest 4-week running volumes were linked to the best weight trends, and the HRV and sleep overlap window did not show a collapse at higher activity levels.
My current answer: this dataset gives me a useful lower threshold for fat loss, but not a reliable upper threshold where training obviously became too much.
VO₂ max and fitness implications
The same general pattern showed up for fitness. When my 4-week running totals got above about 80 miles, VO₂ max tended to improve over the next month.
| 4-week run miles bin | Windows | Avg VO₂ change over 4 weeks |
|---|---|---|
| 0-40 | 4 | 0.50 |
| 40-60 | 8 | 0.31 |
| 60-80 | 20 | 0.17 |
| 80-100 | 13 | 0.38 |
| 100+ | 6 | 0.50 |
That matters because it means the training volume that seemed to help body weight was also generally supportive of fitness.
What I think this means for me
If I want to lose weight: I should treat 20 miles per week as the floor, not the ceiling.
If I want better fitness: that same general running volume seems to support VO₂ max too.
If I worry I am doing too much: my own Garmin data does not currently say that. It says the bigger risk is probably doing too little, too inconsistently.
If I want better recovery: exercise is only part of the system. Late meals, room temperature, stress, travel, and routine disruptions probably deserve just as much attention.
Important confounders
- Late eating
- Hot room or poor bed temperature control
- Overseas travel and jet lag
- Stress and unresolved open loops
- Illness and routine disruptions
Those all affect HRV and sleep, and they can easily blur what looks like an exercise effect. Version 2 of this page should tag those weeks manually.
Bottom line
After 26 months of Garmin data, my best current answer is simple: if I want weight loss, I need sustained running volume, and the threshold seems to be around 20 miles per week.
I do not yet see evidence that my current exercise level is hurting HRV or sleep. The more likely story is that recovery is being shaped by a mix of exercise, food timing, temperature, travel, and stress.
This is an n=1 project, so I am not claiming this is a universal human rule. But for me, this is already actionable.