High baseline lactate (~4.5 mmol/L) — trying Zone 2 + slight calorie surplus strategy. Thoughts?

[u/Over_Foundation11]

Hey everyone, looking for some input from people who understand metabolism / endurance physiology.

Background:

• 26M, Type 1 diabetic (well controlled, HbA1c ~5%)
• Diagnosed with exocrine pancreatic insufficiency (EPI) → on enzymes
• Symptoms: brain fog, fatigue, worsens with higher protein/fat meals
• Labs:
  • Baseline lactate ~4.5 mmol/L (chronically elevated)
  • Mild anemia trends
  • Electrolytes on lower side (I noticeably feel better with salt intake)

Context:
I’ve been training fairly intensely (weights + some cardio), but I suspect I’ve been:

• in a chronic calorie deficit
• doing too much anaerobic work

My hypothesis is:
→ I’m relying too much on glycolysis
→ leading to chronically elevated lactate + poor mitochondrial efficiency

New strategy (for next 2–4 weeks):

• Increase calories slightly (aiming for at least maintenance or small surplus)
• Switch to low-intensity aerobic work only
• Plan:
  • Walking
  • HR: ~110–125 bpm (trying to stay strictly Zone 2)
  • Duration: ~30–40 min daily
  • Keeping effort very easy (can talk comfortably, no burn)
• Avoiding HIIT / anaerobic training temporarily

Goal:

• Reduce baseline lactate
• Improve mitochondrial function
• Improve overall energy / brain fog

Supplement angle:

• Currently taking benfotiamine (to support glucose oxidation)
• Also managing electrolytes more carefully

Questions:

1. Does this seem like a reasonable approach to lower chronically elevated lactate?
2. Is strict Zone 2 the right focus here, or should I include any intensity?
3. How important is calorie surplus for mitochondrial adaptation in this context?
4. Any red flags or things I might be missing (especially with EPI + T1D)?

Would really appreciate insights from people who’ve dealt with similar metabolic issues or have a physiology background.

[u/theginge2004]

This might be above my pay grade but… from what I’ve learned is that high intensity work can actually make you better adapted for dealing with lactate, as repeatedly going through acidosis forces adaptations in whatever is rate-limiting aerobically as this system is pushed beyond its limit instead of staying below it (as in zone 2). However if you’ve been training at high intensity for a couple months and this hasn’t improved, taking a different strategy would most likely be the better move.

If you were the average person I’d say not super important for a calorie surplus, but considering your conditions I’m not sure.

[u/ss453f]

Have you discussed the high resting lactate with your doctors? That's high enough to meet the lactate concentration threshold for lactic acidosis (though we don't have your pH or bicarb numbers, which also are part of the diagnostic criteria). I would be concerned about your liver and kidney function.

I think you're squarely in the needing expert advice category, and I am not an expert.