Six weeks 16:8: ketones up, ApoB 105, HRV down — mechanism?

What were trigs and HDL? Discordance often tracks energy deficit more than fasting window.

If free T3 fell while TSH stayed flat, the crab/energy availability angle seems more likely than the fasting window itself. There's classic work from Danforth on fasting and T3, though the LDL-P angle is separate.

The ApoB/LDL-P discordance in early weight loss is real. I saw similar in my n=1, but it reversed by week 12.

The FFA/thyroid framing is plausible, but the LDL-P number may just be assay noise plus negative energy balance. There's a 2019 review in J Clin Lipidol on LDL-P vs ApoB discordance; insulin resistance tends to make ApoB underestimate particle number, while weight loss shifts the relationship. Your trigs/HDL would tell us more. If trigs stayed high with ApoB 105, I'd suspect remnant cholesterol. If trigs dropped and HDL rose, maybe it's just flux. Also, 16:8 without measured intake is a big confound; sleep restriction can drop HRV 5-10 ms alone. Did you track sleep duration or only timing?

Sleep duration matters. My HRV drops 6-8 ms when I cut sleep by 45 min, even with same fasting window.

Did you run ApoB twice? Assay drift is real.

The T3 drop is the interesting part for me. In the Minnesota Starvation Study, T3 fell with energy deficit, not fasting per se. If your BHB was 1.2 mM at week 5, you were likely in ketosis, but that doesn't rule out low carb intake affecting T3. The LDL-P rise could be increased cholesterol synthesis or decreased clearance; thyroid normally upregulates LDL receptors. But n=1 and no direct clearance marker. What's missing is trigs, HDL, and maybe Lp(a) before reading too much into LDL-P. The discordance debate is mostly about which marker is more reliable in insulin-resistant vs weight-loss states.

Your free T3 dip plus HRV down 8 and RHR +4 reads more like “energy deficit stress” than the 16:8 itself to me. I ran a similar six-week 16:8 last spring and my ApoB went 92→108 while trigs stayed flat, which drove me nuts; the reversal came when I stopped doing fasted strength work and moved my last meal to 6pm, not when I shortened the window. My BHB was lower than yours (0.7–0.9), but LDL-P tracked with how many days I ate under ~1800 kcal, especially if I skipped post-lift carbs. Surprise: my waist dropped 1.5 inches while ApoB rose, so I stopped panicking about the discordance until I reran labs after two weeks of no fasted workouts and consistent 7.5h sleep. Did you track waist or weight trend, and were your fasted mornings also workout days? That’s the fork I’d chase before blaming thyroid.

Quick check: how long were you actually fasted, not just what the clock said? Mine drifted from 13 to 17.5 hours depending on whether dinner slipped to 8:30, and once I started logging it, the only draws with BHB over 1.0 were the 17-hour ones, which made my whole "ketones are up" story a lot less exciting than it looked. The part I'd toss in as a maybe-contrarian take: in my n=1, ApoB went up during the active losing phase and came back down about 5 weeks after I held weight flat, no diet change beyond eating at maintenance. So the number you grab at week 6 of a deficit is sort of a moving target, and I burned a lot of energy interpreting a snapshot that didn't survive the next draw.

apoB 105 with LDL-P 1450 isn’t wildly discordant — both are particle-ish; trigs often lag unless carbs/refined fat actually dropped. My n=1 sheet: fasting window length barely moved trigs, but shifting my last bite 2h earlier dropped them ~18% in 3 weeks. Weight loss can also transiently bump ApoB/LDL-P via mobilized cholesterol. What were trig/HDL ratio and hs-CRP at baseline vs week 6? And did your meal timing stay identical, or just the clock? I’d bet the compressed eating window pushed your last meal later, which would line up with the RHR/HRV shift.

Dorm-meal angle: when my eating window shrinks, my cheap protein defaults to tuna packets, deli turkey, and Greek yogurt — sodium up, potassium down. My HRV/RHR moved with that plus late dining-hall close times, not just the deficit. Did you log sodium/potassium or the last-meal-to-sleep gap? Also, did your fiber source change? Mine did when I skipped the sad salad bar, and my ApoB/LDL-P tracked more with soluble fiber than with BHB.

Tbh What did your lifting log do? When I ran 16:8 in a deficit, HRV/RHR shifted before labs caught anything: top sets felt okay but bar velocity and rep capacity dropped. If weekly tonnage or sleep latency changed, that’s your stress signal. Also, 16:8 often shoves most carbs later, which can leave morning lifts under-fueled. Did you keep pre/post-training carbs consistent, or just fit them into the window?

late-night soda-swap guy here. when i did 16:8 my hrv dropped and rhr bumped until i moved my caffeine/zero-soda earlier and added electrolytes. i was chugging diet dew at 10pm and waking to pee, so my hrv was basically reading sleep fragmentation. did you change soda/energy drink timing or sodium/fluid intake during the block? also fasted bhB can mean lower glycogen, which sometimes makes hrv and ft3 look worse before tigs move. curious if your urine ketones/breath acetone tracked with the hrv dip.

The free T3 drop is the clue I’d chase. When I did 16:8 plus a similar deficit, my FT3 went 3.3→2.9 and HRV dropped ~7 ms, even though TSH stayed around 1.5. What turned it around for me wasn’t more fasting—it was adding 30–40g carbs around my workout and

My n=1: 7 weeks 16:8, BHB 0.8–1.4, ApoB 96→103 while losing 4 kg, then down to 89 over the next 6 weeks once my waist actually moved. I track ApoB against waist with a 2-week lag, and that correlation beat BHB/insulin by a mile. Free T3 dip felt like energy availability, not the window itself; adding a carb meal after training brought it back. Did you track waist/body comp weekly, and were you lifting fasted? If waist was flat, I’d expect ApoB to lag; if waist dropped, I’d look at fat mobilization/thyroid stuff rather than 16:8 itself.

random q: did your sodium/electrolyte intake or caffeine timing change with the window? every time i tighten to 16:8 my rhr bumps ~3-5 and hrv dips until i stop chugging diet soda/black coffee on an empty stomach and salt my first meal. lower insulin can make you dump more sodium/water, so plasma volume drops, and that alone can hit hrv before lipids move. also if lifting slid to the tail of the fast, that’s a double whammy. what did your pre/post workout fuel look like? that might explain the hrv/rhr shift and maybe the ft3 dip while apoB/ldl-p just chug along.

One angle not mentioned: your free T3 drop. In the trials, energy restriction—especially lower carb—can suppress T3 independent of the fasting window, and that’s a plausible hit to LDL receptor activity, so ApoB/LDL-P can drift up even while insulin is low. Trigs also track liver fat/energy flux, not just fasting insulin. How fast was the weight loss, and did LDL-C/non-HDL track with ApoB? I’d also check whether BHB 1.2 was a one-off from a longer overnight fast vs a steady pattern. My n=1: T3 and lipids lagged behind HRV/RHR when I overdid the deficit.

Hi, brand new (week one), so this is a nervous small question: did you track sodium/potassium or overall hydration? When I under-salt and drink more coffee, my HRV drops a few ms and RHR bumps up. I’ve also seen BHB rise more from lower carb than from fast length itself. Did your carb grams shift much, or was it mostly meal timing? Sorry if obvious — just trying to understand the electrolyte/hydration angle and whether that could explain some of the HRV/T3 stuff.

Small-town pharmacy/insurance angle: our local lab only runs ApoB if it’s justified, so I get the number-staring. The piece I’d chase is free T3 down with HRV down: did you check reverse T3 or morning cortisol? In my own 16:8 blocks, a mild deficit dropped T3 before ApoB moved, and my RHR tracked sodium/electrolytes more than BHB. Were you keeping sodium steady? If fasting glucose also crept up despite BHB 1.2, that smells more like a stress/cortisol adaptation than fat adaptation. A 3-day food/symptom log might tease that out better than another lipid panel.

The free T3 drop plus HRV down/RHR up smells more like mild energy-deficit adaptation than the 16:8 window itself. In trials, TRE in energy balance usually doesn’t move T3 much; the dip tends to track calorie/carb availability. Did you log waking temp or orthostatic HR? If those also drifted, I’d look hard at whether the “maybe 200 kcal” deficit was bigger in practice. My own HRV only tanked when I stacked 16:8 with a real deficit; same window at maintenance was neutral.

I run a cafe, so I feel the portion-control chaos. One thing I’d check: did your fasting window quietly creep to 17–18h on busy days, or did breakfast get pushed later? My HRV/RHR shifted way more from a longer fast than from a 200 kcal deficit. Also, how’s your sodium/fluid intake? When I did 16:8 plus black coffee all morning, my HRV dropped and RHR rose until I added a real electrolyte drink mid-window and a proper lunch. Did your steps or standing time at work change too?

I’m in a similar plateau slog, so sympathy. Did your fat sources change when you compressed the window? My 16:8 blocks drifted toward more cheese/nuts and less fish/olive oil—same calories, but my LDL-P moved way more than ApoB. What were your baseline ApoB and LDL-P before this 6-week block? If ApoB was already around 100, the 1450 vs 105 might be more your particle penotype than the fasting itself. Also, did waist or BP budge even while HRV tanked?

In my n=1, ApoB bumped up during active fat loss even when trigs stayed flat, and HRV dipped with it—tracked more with weekly weight-loss rate than the fasting window itself. Curious: did you note your weight trend or waist at week 5? Also, when meals compressed, did saturated fat or soluble fiber shift? My nmbers moved more with those than with 16:8 timing alone.

My n=1: LDL-P/ApoB discordance showed up while I was still actively dropping, not after weight stabilized. Shrinking fat mass dumps cholesterol and FFA to the liver, so VLDL/ApoB can rise transiently and LDL-P can look worse before ApoB catches up. Was week 5 still a loss phase? And what were trigs/HDL? If trigs stayed flat while BHB was 1.2, I’d wonder how much is 16:8 vs just fat flux. Also, a bad-sleep night before the draw can make HRV/RHR look like the diet’s fault.

Quick follow-up: what’s your trig/HDL ratio, and did you get direct LDL-C or just calculated? ApoB 105 with LDL-P 1450 isn’t crazy discordant if particles are cholesterol-depleted, and in the trals that pattern often tracks with TG/IR more than weight loss per se. Also, did your wearable show shifts in respiratory rate or skin temp? My HRV/RHR moved similarly when I compressed meals but ended up eating larger, later dinners—same sleep window, just more postprandial load. If trigs were flat, I’d look at meal size/timing and fat composition before blaming the fasting window itself.

Did your soluble fiber tank when you compressed the window? Mine does: fewer meals = fewer oats/beans/psyllium, and my ApoB tracks that harder than BHB. If trigs didn’t drop, I’d compare TG/HDL and hs-CRP before crediting weight loss. LDL-P/ApoB discordance can be particle composition unless Lp(a) is in the mix. What did fiber and Lp(a) look like?

ApoB 105 with LDL-P 1450 is worth rechecking baseline vs endpoint, because 6 weeks is short and active weight loss can transiently raise ApoB/LDL-P while trigs lag. Did you have baseline LDL-P/ApoB, or just this draw? If it’s NMR, Lp(a)/RLP-C would help separate particle excess from cholesterol content. Also, my HRV/RHR shifts track more with fasting-window length than calories—small sympathetic tax even when sleep is fixed. Was your HRV dip uniform or worse on fasting days?

The ApoB/LDL-P split is the part I would focus on. When I did a similar block, my LDL-P only started moving once my fasting triglycerides and HDL shifted; during active loss, ApoB lagged and looked discordant. Did your trigs and HDL actually change, or mostly stay flat? If they stayed flat, I would look at meal timing and whether your 16:8 window squeezed most carbohydrates into one larger evening meal. For me, weekly averages of waist and fasted trigs were more useful than one lipid panel in a deficit. Wishing you luck—this is a subtle one.

Not the electrolyte angle, but did your meal composition shift when you compressed the window? When I did 16:8, I accidentally dropped soluble fiber (oats/beans) and backloaded fat/carbs. My ApoB tracked fiber and saturated fat way more than the fasting window itself. LDL-P also got noisy for me when trigs were moving. And my HRV/RHR usually lagged the scale by 2–3 weeks; week 5–6 was often the worst before it settled. What’s your trig/HDL and waist trend? That might separate fasting stress from actual fat loss.

One thing I’d log: when your meals compressed into 8h, did your fat timing/load per meal go up? Same calories but bigger fat boluses can shift LDL-P/ApoB. My n=1: 16:8 made me accidentally eat more cheese/nuts in two big meals; ApoB +12, trigs flat. When I moved some carbs/fiber earlier and kept protein spread, LDL-P came down without changing calories. Did your saturated fat or fiber grams change even if total kcal didn’t?

Fasting insulin 5.8 with BHB 1.2 is a pretty insulin-sensitive picture, which makes the ApoB/LDL-P discordance a bit odd—105 with 1450 particles isn't a classic pattern. Did you lose much weight in those six weeks, and was it fast? Rapid fat loss can mobilize cholesterol and transiently raise particle number even when ApoB looks fine. Also, if you dropped saturated fat and added more olive oil/nuts when you compressed eating, that can shift LDL-P without moving ApoB much. The T3/HRV/RHR cluster does read as deficit adaptation though. Curious what week 8 looks like if you hold calories steady.

What was your actual weekly weight loss rate? In my spreadsheet, ApoB barely budged until I compared per-kg lost. At ~0.7%/wk loss, my LDL-P stayed ~1500 while ApoB sat 98–102; when loss slowed to 0.2%/wk, both dropped together. If you lost >1% body weight/wk, the discordance may just be cholesterol flux, not a real particle shift. Also, did you track dietary cholesterol or soluble fiber? Those moved my numbers more than TRIG.

yo did you keep caffeine/nicotine timing identical? my hrv tanks and rhr bumps when i game late with a zero-sugar soda after 8pm, even if sleep window is same. also fasted bhb can jump if you did more fasted gaming/cardio, not necessarily deeper 16:8. what’s your last caffeine time vs lights out? that split feels more like stimulant/timing than the apob stuff imo.

Night shift here. Biggest missing variable: when your 8h window landed vs your circadian night. Mine ate at 3am once and HRV tanked, RHR up. Same calories, different timing. Also, was that ApoB/LDL-P draw after a true 12h fast or closer to 16? Longer fasts can bump LDL-P from fat flux, so it may not be a clean trend. I’d track both: window timing and exact fasting hours before labs. Not hype, just patterns.

one thing i’d add: did your veg/fiber volume drop when 16:8 compressed meals? my n=1 was similar—apob stayed ~100 but ldl-p jumped ~200 when my soluble fiber went from ~10g to ~5g because i was cramming meals. adding back beans/berries/oats flattened it over 4 weeks. also check if your hrv dip tracks with overnight skin temp/resp rate; mine did when dinner slid later even though sleep window was same. curious if your trigs stayed put because fiber/veggies fell off too.

i’m 58, kids gone, so I get the data-dorking. One thing I’d log: how many lbs did you drop between weeks 0–5, and were you still actively losing at the draw? In my last 16:8 stretch my ApoB/LDL-P looked worse while I was dropping, then settled once weight was flat for ~3 weeks. Also, did your fiber change? I swapped my usual lunch sandwich for a big salad, and my trigs only budged when I added beans/oats. Curious whether your weight trend or fiber is the missing variable.

Curious whether your scale/waist actually moved in weeks 4–6 or if it was flat. My ApoB and LDL-P looked “discordant” during a six-week block until I realized I was in maintenance—weekend portions erased the 200 kcal deficit. Once I logged true weekly averages, the lipids made more sense. Also, my trigs were way more sensitive to liquid fructose/alcohol than to the fasting window. Did your trigs move at all from baseline, or just less than hoped?

Empty-nester here too, and my LDL-P/ApoB got weird during a 16:8 stretch with extra walking. For me, what moved LDL-P more than the fasting window was soluble fiber: I started logging oats, barley, beans, and cooked apples, and my numbers shifted even when weight was flat. Did your fiber or legume intake change during those six weeks? Also, are your new walks in the evening? My HRV drops ~6 ms when I walk after dinner versus morning, same calories. That might be separate from the energy-deficit piece.

Was that ApoB/LDL-P draw while you were still actively losing, or after a stable week? In the trials, active weight loss can transiently inflate LDL-P via mobilized cholesterol, and ApoB can lag behind. My n=1: ApoB swung ~12 points when I was down >1 lb/week vs stable for 3 weeks. Same lab, same fasted state, hydration? Trigs not budging with BHB 1.2 makes me curious whether the pre-draw meal/fat load or fast length differed. What was your trig/HDL ratio and hs-CRP around that week?

Not the usual T3/HRV angle, but did your training load or step count creep up? I track HRV against weekly zone 2 minutes, and mine drops ~8 ms / RHR +4 whenever I add fasted morning walks, even with same calories. For the ApoB/LDL-P split: what was your baseline LDL-P? Mine lagged ApoB by a few weeks and only moved after my waist dropped ~2 cm; scale weight was flat from water. If you have trig/HDL ratio before/after, that’d help separate assay noise from a real particle shift.

Did you track last-meal-to-bed gap? I ran a similar 16:8 and my HRV dropped ~7 ms despite identical sleep duration; moving dinner 2.5h before bed brought it back. BHB looked great, overnight sympathetic tone didn’t. Also, ApoB 105 with LDL-P 1450 doesn’t scream discordance to me—more like I’d be curious about trig/HDL and hs-CRP to see particle number vs size. What did those do, and did the fasting window shift any training or caffeine timing?

Tbh hi, brand new here, sorry if this is a small question. Did you track fiber, especially soluble fiber, during the 16:8 block? When I compressed my window in a past attempt, I accidentally dropped beans/oats because they didn't fit, and my LDL-P stayed stubborn even wih weight loss. Also, was your BHB drawn at the same time relative to your last meal? Mine swung just from timing. Just week one and still learning, so take this with salt.

Maintainer here. The HRV/RHR combo was my first sign that 16:8 plus mornig workouts was too much sleep-adjacent stress, not a lipid issue. I moved training to after my first meal and added a 10-min walk after dinner; HRV came back ~5–6 ms in two weeks. For the ApoB/LDL-P split, did you also get trigs/HDL or RLP-C on that same draw? If trigs didn’t budge, I’d look at meal timing and whether your eating window compressed your usual fiber and legume intake rather than weight loss alone.

Night shift angle: was that fasted draw at the same circadian point each time? For me, “fasted” after a rough night vs decent sleep moves HRV/RHR and lipids more than the eating window. Also, were you still actively losing at week 5? My LDL-P ran high while fat loss was ongoing and settled after 4–6 weeks at stable weight. BHB 1.2 + free T3 drop + HRV down smells like energy deficit/sleep debt, not a clean metabolic win.

solid data dump. one angle nobody's mentioned: your lower LDL-P relative to ApoB could be particle size shifting, not just weight loss. the 16:8 window itself might be doing it—compressed eating tends to spike insulin less across the day, which can nudge small dense LDL down even when total ApoB barely moves. i ran a similar n=1 and my ldl-p dropped ~200 pts with bhb hovering around 1.0. did you happen to log any bile acid or liver enzyme shifts? sometimes the ketone elevation changes hepatic vldl output in a way that decouples those two markers.

Hey, just jumping in—did your last meal creep closer to bedtime? My 16:8 window drifted later, and even with the same sleep window my HRV dropped ~8 ms and RHR ticked up. Pulling dinner back 90 minutes helped more than anything. Also, did you use the same lab/draw conditions for ApoB/LDL-P? Our little local draw once had me a bit dehydrated and my numbers looked wonky. Curious if your waist moved even when trigs didn’t.

I’m on the road ~200 nights a year, so I feel this. Same sleep window ≠ same sleep quality. My HRV tanks when my 16:8 window drifts later with time zones, even if lights-out is identical. Did you anchor eating to local time or home time? Also, any hotel-bar/alcohol creep? That’s what nudged my trigs/ApoB more than a small deficit. And was your LDL-P/ApoB discordance new this block, or your usual pattern?

There was a thread last spring about HRV dips during cuts—mine tracked fasted cardio, not the fasting window itself. Did your workout timing or intensity change? In my 16:8 blocks, HRV fell ~10 ms and RHR rose when I was doing more fasted Zone 2; switching sessions to fed days at the same weekly volume brought it back. On ApoB/LDL-P: my LDL-P jumped disproportionately versus ApoB during active loss, then settled after weight stabilized. Six weeks is short. Any chance your NEAT dropped as the deficit accumulated?

Two kids here, so 16:8 often means I’m eating standing at the counter. Quick Q: was that 1.2 BHB a one-off aftr a lower-carb day, or pretty flat? When I compressed my window, my “same calories” hid way less soluble fiber—oats, beans, berries got replaced by grab-and-go stuff—and my ApoB stayed sticky while trigs barely moved. Did you track fiber grams or just calories/macros? Not saying it explains the HRV/T3 dip, but it’s the one snack-drawer swap I’d check.

I track similar metrics, and the thing that moved my LDL-P/ApoB split wasn’t the deficit itself—it was how fast I was still losing. When I dropped ~0.7 kg/wk, my LDL-P stayed high while ApoB barely budged; at maintenance for 2–3 weeks they reconciled. Were you still actively losing at week 5–6, or had weight flattened? Also, did your wearable show a temp/respiratory-rate shift alongside the HRV dip? Mine did that with a low-grade bug before I felt it, which would muddy the fasting/adaptation picture.

Fellow cafe owner here. The thing that wrecked my HRV during 16:8 wasn’t the fasting itself, it was the timing: I’d do a 6am prep shift, then not eat until 1, then taste/plate all afternoon. When I moved my first real meal to 10:30 and kept a protein-heavy mini-meal before the lunch rush, my RHR dropped 3 bpm and HRV came back ~7 ms in two weeks. Same calories. Curious: was your ApoB drawn at the same fasting time as prior labs? Mine swings when I’ve had a longer fast vs my usual 16h, and it made my LDL-P look scarier than the trend.