This gets cited here weekly, usually second-hand, so it is worth setting out what it does and does not establish.
A sustained drop to 1,100 or 1,200 calories reliably under-delivers a predictable set: B12, vitamin D, iron, folate, zinc and magnesium. Two of those are worth testing rather than guessing because the tests are cheap and the symptoms overlap with everything else — ferritin and B12. The rest a decent multivitamin covers, and there is no benefit in megadosing any of them.
Where I think it is weakest: the population was selected and supported in ways a real cohort is not, so I would read the effect size as a ceiling rather than an expectation.
What I actually want to know is which deficiencies actually show up when intake drops this far, and which are worth testing rather than supplementing blind. If the honest answer is that nobody knows, that is a useful answer and I would rather have it.
Figures above are from the primary publication rather than the press summary. If a number here disagrees with one you have, post yours and we will work out which of us is reading a secondary source.
BethLabQueen said:A sustained drop to 1,100 or 1,200 calories reliably under-delivers a predictable set: B12, vitamin D, iron, folate, zinc and magnesium.
Vitamin and mineral labs to check while on micronutrients — my doctor orders these quarterly:
- B12: Can drop due to reduced GI absorption. Mine went from 650 to 380 — now supplementing.
- Iron/Ferritin: Reduced food intake = reduced iron. Ferritin dropped from 56 to 23. Supplementing.
- Vitamin D: Was already low (23 ng/mL), now taking 5000 IU daily.
- Folate: Stable, no issues.
- Zinc: Slightly low, added a multivitamin with zinc.
Nutritional deficiencies are a real risk when you're eating significantly less. Don't skip your labs!
BethLabQueen said:A sustained drop to 1,100 or 1,200 calories reliably under-delivers a predictable set: B12, vitamin D, iron, folate, zinc and magnesium.
Vitamin D levels and micronutrients: an often-overlooked connection. Obese individuals store vitamin D in adipose tissue, making it less bioavailable. As you lose fat, vitamin D can actually increase WITHOUT supplementation.
My trajectory: Baseline 18 ng/mL → Month 6 (with supplement) 42 ng/mL → Month 12 48 ng/mL. Target is 40-60 ng/mL. Adequate vitamin D supports immune function, bone health, and mood — all relevant during weight loss.
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View ResultsJessicaH_TX said:Vitamin D levels and micronutrients: an often-overlooked connection.
Blood count monitoring for micronutrients: my doctor noticed my MCV (mean corpuscular volume) trending up at month 6: 88 → 98 fL. This flagged potential B12 or folate deficiency.
Sure enough, B12 had dropped from 620 to 340 pg/mL. Started B12 injections monthly and MCV normalized within 2 months. GLP-1 agonists can impair B12 absorption — this is a real clinical concern that deserves routine monitoring.
BariatricNurseD said:Vitamin and mineral labs to check while on micronutrients — my doctor orders these quarterly: B12: Can drop due to reduced GI absorption.
Second this.