How I lost the fat without melting muscle.

• Weight

  175 lb→160 lb−8.6%

• Fat

  23%→11.7%−49.1%

• Lean mass

  77%→86.7%+12.6%

Withings, April → end of August 2026. Same story as Protocol Results.

1. 01 · Cardio

   Fatmax at 120 bpm.

   What I’m doing

   Aim

   120 bpm — one number, not a range. Easier to lock mid-session than a band I have to babysit.

   Floor

   2× / week × 40 min. That is the minimum I protect. I try to beat it when recovery allows.

   Extras

   A weekend session if there are no family plans. Sometimes after strength if I still have energy.

   How

   Low-impact so I can think. Podcasts every time. Treadmill walk by default, elliptical about 25% of the time, stairmaster sometimes.

   Constraint

   I would rather walk or jog outside, but there are no sidewalks here and it is flat, so BPM will not hold. I am looking at a weighted vest for outdoor Zone 2.

   Why 120. Pick your number.

   Here is the research path that got me to 120 — and a simple table so you can pick yours. Try it 3–4 weeks and tell me how it goes.

   The treadmill still labels a “fat-burn zone” at an easy effort because a bigger share of those calories come from fat. That percentage chart is true, and it is the wrong question. At a stroll you might be mostly fat-fueled and barely working. The honest chart is grams of fat oxidized per minute. That peaks at moderate intensity — Fatmax — around the top of Zone 2.

   

   As effort climbs, carbohydrate takes a larger share of the mix. Zone 2 is the plateau where fat is still the main fuel and total work is high enough that the grams add up — and low enough that I can do it again this week. The lab version of that mix is respiratory exchange ratio: about 0.7 when you are oxidizing fat, about 1.0 when you are on carbohydrate.

   

   In-session fat grams keep rising if you stay on the machine for two hours. Recovery does not. A 150-minute hero session is how you skip Thursday. Forty minutes is the floor I protect: long enough to spend real time at Fatmax, short enough that two sessions a week actually happen.

   

   Pick your number.

   Estimated max HR = 220 − age. Zone 2 is 60–70% of that. The target I use is 70% — then I lock one number. Mine sits around a 178 max, so 70% is about 125. I aim at 120.

   Table A · by age

   Zone 2 heart-rate targets by age using 220 minus age

   Age	Est. max HR	Zone 2 (60–70%)	Target (70%)
   30	190	114–133	133
   35	185	111–130	130
   40	180	108–126	126
   45	175	105–123	123
   50	170	102–119	119
   55	165	99–116	116
   60	160	96–112	112

   Table B · if you know max HR

   Zone 2 heart-rate targets from a known maximum heart rate

   Max HR	Zone 2 (60–70%)	Target (70%)
   170	102–119	119
   175	105–123	123
   ~178 (mine)	107–125	120
   180	108–126	126
   185	111–130	130
   190	114–133	133

   ~178 max → I aim 120. One number I can see on a watch without doing math mid-stride. It still sits in Zone 2.

   Sources

   • Heart rate training zones

     The 60–70% Zone 2 band, and why max HR estimates are a starting point.

   • Zone 2 training

     Aerobic work, fat as principal fuel, and the usual 60–70% max-HR definition.

   • Achten & Jeukendrup, Fatmax (2002)

     Open PubMed abstract: the intensity where fat oxidation peaks, often near the top of Zone 2.

   • Respiratory exchange ratio

     RER ~0.7 is mostly fat. RER ~1.0 is mostly carbohydrate.

2. 02 · Protect muscle

   Protein + lift.

   What I’m doing

   Lift on the Base Protocol schedule — strength about three days a week. Keep protein high enough to hold lean while cutting. The exact grams stay on the protein + food pillar; this page is the reason that pillar exists on a cut.

   Daily burn above intake, without building or protecting muscle, can pull from lean tissue. The goal is not “work harder empty.” It is a deficit with muscle protected. That is why the scale drop looked so fast without melting muscle.

   

   Sources

   • Strength training

     The signal to keep — and later build — lean mass while you cut.

   • Weight loss

     Scale weight is a mix. Fat and lean do not have to move together.

3. 03 · Weekly deficit

   Sustainable. Nothing heroic.

   What I’m doing

   Eat a bit less than I burn. Macros in ratio, a small deficit — the same story as the nutrition pillar. Less junk. I do not live at 150-minute sessions to “earn” fat loss.

   Session fat grams are not the scale. The week is. Zone 2 supports the deficit; food is still the main lever. Protect the 40-minute floor so the cardio actually repeats. Do not turn one long session into the whole plan.

   Sources

   • Calorie deficit

     The week is the unit. Session fat grams are not the scale.

   • Food energy

     Energy in versus energy out, without turning it into a religion.

This is personal tracking, not medical advice. I am sharing an N=1 scorecard so the work is visible — not a protocol to copy blindly. Read Bryan’s protocol at the source, and talk to a clinician who knows you.