30 days no added sugar: deep sleep up, mood flat

2026-09-05 10962 views 93 posts

I just wrapped a 30-day no-added-sugar stretch. I'm not diabetic, just curious.

My tracker says deep sleep went from 48 min to 59 min average, resting HR down 4 bpm, and my fasting glucose on a home meter dropped from 104 to 92. But my mood is flatter and workouts feel harder. I expected to feel amazing.

Anyone run a similar n=1 and find the sleep numbers lie? Or is this just the adaptation dip?

Curious what data you'd track next.

The flat mood is the part I'd dig into. When I did a no-sugar month, my HRV dropped for two weeks before rebounding. Did you keep training load steady?

Same here, deep sleep up but gym RPE felt tw opoints harder. I added rice before lifting and the flatness lifted. Not saying it's magic, just my n=1.

Rice isn't the same as the added sugar I cut. Timing around workouts changed how I felt, even with fasting glucose staying at 93.

I ran a six-week no-added-sugar stretch and logged CGM. Fasting glucose went 101 to 94, and my sleep score improved mostly in the first ten days.

Weeks three and four were rough: low motivation, harder intervals, and I was definitely under-eating. What helped was keeping protein high and adding carbs around training, not cutting total carbs to zero.

If you're flat at day 30, I'd check total calories and training volume before blaming the sugar change. The deep sleep bump can be real and still not enough to offset underfueling. That was my experience, anyway.

My flat mood during a sugar reset turned out to be low iron on routine labs. Totally unrelated to sugar.

Tracking mood and energy at the same times daily is worth the effort. Deep sleep moved in the right direction, but the 3pm slump got worse, and that lined up pretty clearly with eating less overall.

What app are you using for deep sleep?

I did a 21-day no-added-sugar stretch last spring and my tracker showed deep sleep up about 8 minutes and resting HR down 3, but my mood was gray and squats felt like sandbags — the surprise was it wasn’t sugar withdrawal, I’d accidentally dropped ~40g total carbs and 250 calories by cutting flavored yogurt, granola, and my usual post-gym chocolate milk. Once I kept the no-added-sugar rule but added a plain baked potato with dinner and a banana before lifting, my mood came back in about 4 days and my top set went from 125 to 135 again while sleep stayed good.

If workouts feel harder, I’d look at total carbs/calories and caffeine timing before blaming the sleep numbers — are you eating enough around training, or did you also cut back on coffee/tea?

Your sleep numbers are probably real, but the flat mood and grindy workouts smell like under-fueling, not sugar withdrawal. I did a month of no sweetened coffee, cereal, or dessert and my sleep score went up about 8 minutes, but I felt like crap until I actually looked at intake and saw I’d dropped ~400 calories/day without meaning to; since I started, it’s stupid easy to under-eat because nothing sounds good.

The weird fix was adding a banana or dates before lifting and 30g protein at breakfast, which is technically still no added sugar, and my mood came back around day 8-10 while my squat reps stopped feeling like sandbags. Have you checked total calories/protein, or just the sugar line?

That’s where I’d look before calling it an adaptation dip.

I ran a similar 30-day no-added-sugar experiment and saw the same split: deep sleep +8–10 min, RHR down, but mood and gym sessions felt dull. For me the missing variable wasn’t sugar, it was sodium and carb timing.

Cutting sweet snacks/sauces also cut a ton of incidental salt, and my harder sessions felt flat until I started salting meals and eating most of my carbs around training. Sleep stayed good. Did your sodium intake or workout-day carb timing change much, or was added sugar the only thing you pulled?

Also, are you looking at 7-day rolling averages or single days? The daily mood noise lies.

did you track total carbs or just added sugar? I did a dorm “no added sugar” month and accidentally replaced desserts with low-fat/nonfat stuff, so calories were fine but my pre-lift snack was a rice cake and a prayer.

My mood tanked until I added fruit around workouts and a cheap egg/tuna scramble. Curious if your carb timing shifted, especially before training—because my flatness was way more about when carbs showed up than the sugar itself.

For wat it's worth, new here too, only week one, but rooting for your mood to catch up with that sleep win!

For what it's worth, man, same—sleep score up, mood in the gutter, and squats felt like wet sand. Recomp is a troll lol.

Optimization problem: you changed one variable but probably moved three. I had the same flat-mood/grindy-workout thing after cutting added sugar—turned out I’d also dropped total carbs and sodium.

Sleep stayed great, but mood and RPE recovered when I kept fruit/potatoes around training and salted meals normally. Did your total carbs/calories/sodium stay flat? If not, you didn’t test no-added-sugar; you tested low-carb + low-sodium.

I ran a no-added-sugar month last fall and got the same split—sleep great, mood blah. What cracked it for me was realizing I missed the ritual, not the sugar. The 3 p.m. cookie was my little reset button.

I swapped in a fancy tea and a 10-min walk, and after about two weeks the flatness faded. I also kept frozen mango in the freezer for when I wanted something sweet; still no added sugar, but it kept me from feeling deprived.

Did you drop any sweet ritual cold turkey, or was it more of a total sugar sweep? That might explain the mood vs. sleep mismatch.

Same split here: sleep great, workouts grindy, mood very beige. My spreadsheet is smug; I am not.

Same n=1 here: sleep was elite, but my mood ran flat and squats felt like tax season.

I had a similar split, but I think mine was more about the routine than the sugar itself. My after-dinner walk plus cutting my little evening treat improved deep sleep, yet mood felt flat because I’d deleted the cozy ritual and didn’t replace it.

Now it’s herbal tea and 10 pages of a library book—same wind-down cue, no added sugar. Workouts also felt grindy until I noticed I’d stopped having a banana before my morning walk.

Did your meal timing or pre-workout routine change too, or was sugar the only variable?

same here—great sleep, flat mood, gym felt like molasses. I just logged it and moved on, ha.