In this segment of the "What’s Up with Water Fasting?" interview, the speakers examine how intermittent fasting (IF) and water fasting affect weight loss, hormonal balance, sleep, hair health, and skin elasticity, especially in women and individuals with significant excess weight. They note that daily IF often yields an initial surge of well‑being that wanes after about six weeks, with women reporting poorer sleep, menstrual irregularities, and temporary hair thinning. The discussion attributes these symptoms to rapid weight loss‑induced neuroendocrine changes—particularly elevated cortisol and altered thyroid function—that stress hair follicles and disrupt sleep. Dr. Goldhamer explains that the hair thinning is a reversible, non‑follicular loss caused by nutritional stress, and that normalizing cortisol and thyroid levels restores hair growth. He also contrasts water fasting with high‑protein diets, suggesting that water fasting leads to less skin sag and a milder hormonal shock because the weight loss is less abrupt. The speakers recommend a moderated IF schedule (e.g., three‑to‑five days per week with a protein‑rich, healthy‑fat breakfast) to allow the body to acclimate to fasting stress before moving to daily fasting.
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Here's the caveat, and this is something that I've really looked at over the last 10 years, because intermittent fasting has been a core part of the bulletproof diet. The book came out in 2014, but I started publishing it in 2011. And what I find is that especially people who have a lot of weight to lose, who haven't done long term fast, like, like you do at your clinic, if they start doing intermittent fasting every day, they feel amazing for the first couple weeks. But then, and women hit the wall first, they typically say, wow, my sleep quality just started declining and I don't know why. And then my cycle's off and then my hair starts thinning. And it usually takes about six weeks of everyday intermittent fasting. And usually they'll say, I feel so good, I'm just gonna go to one meal a day. And what I found is that especially for women, but also for men with a lot of weight to lose, intermittent fasting three days, five days a week, but then having a morning breakfast. In my experience, you would want a higher protein, higher healthy fat, not higher, any fat breakfast. But maybe you could do it with a high starch, low fat approach. It probably would work. But you do that sometimes partly to keep the metabolic flexibility high, but, but also because fasting is a hormetic stressor and I think they just get overstressed until they become acclimated to fasting and then they can start doing everyday intermittent fasting.
Right. Remember though that anytime there's rapid weight loss, there's hormonal changes, whether it's pregnancy or whether it's fasting or if you increase activity significantly. Anytime there's rapid weight loss, there are changes and you may be right. These are maybe neuroendocrine mediated or others that be associated with temporary hair thinning. You don't lose any follicles. What's happening is hair, you're under nutritional stress, the body affects the hair growth. There's some conservation, everything comes out together. So there's what looks like thinning. Overall, hair integrity is maintained if thyroid function is normalized.
I think it's a cortisol issue. Cortisol's in the correct because that affects the sleep and then the thyroid. And when the cortisol goes back down, the hair follicles should come back. And they do every now and then.
It doesn't happen a month post long term fasting. You'll see this phenomena frequently when there's been a lot of weight loss. So I think what you're doing is anything you do to modulate how rapid that initial weight loss is, probably modulates. I don't know that it's necessary because it's a temporary phenomena. It's not associated with decreased physiological function. It's just, this is one of the things that happens. And it's just like, initially there's more skin sag until the body's able to recover. There's less of that with water fasting than there is with, say, high protein diets.
