The hormonal difference between eating less and eating less often.
What the evidence says
- Fasting: norepinephrine increases 117%; resting energy expenditure increases ~14% — *`caf02`, the larger study, qualifies the second: RMR up ~6% at 36 h, no longer significantly above baseline at 72 h (P = 0.06), and not significantly changed in men* — both figures are `caf01`'s measured values (1716 → 3728 pmol/L; 3.97 → 4.53 kJ/min), and `cif01` relays them at the two pages given[1],[2],[3]
- Fasting: 5-fold increase in growth hormone production rate by day 2[4]
- Calorie restriction: Daily caloric restriction does lead to decreased metabolism (Minnesota Starvation Experiment model)[1]
- Minnesota Starvation Experiment (1944-45): *36 men entered and 32 completed — the reported findings rest on the 32. They ate an average of 1,570 Cal/day, roughly half of normal, for 24 weeks, losing 24.24% of body weight against a 25% design target; total basal metabolism fell by about 40%*, which is the book's own phrase for its own experiment[5]
- Minnesota physical changes: basal pulse rate fell to a mean 40.8 beats/min by week 5 and a minimum average 35.3 at week 13; basal respiration rate 11.45 → 9.86 per min and basal pulmonary ventilation −30.6%; body temperature showed *a small decrease* — the book's own characterisation, and smaller than the cardiac and respiratory changes[5]
- Minnesota psychological symptoms — *apathy, obsessive food thoughts, depression, irritability — are first-hand since 2026-09-01, Volume II having been acquired. The book calls the syndrome "semi-starvation neurosis"*. `cdi05` reports the same symptoms independently and remains a good co-citation[5],[6]
- *"Hysteria" is NOT among them. It appeared in `cif05`'s symptom list until 2026-09-01 and is an MMPI scale name* (Vol. II, Ch. 40), not an experience the men reported[5]
- Calorie restriction physiological effects: heart rate *−14%, energy cost of walking −22%, SNS activity −38%*[7]
- *What those adaptations do not explain is adaptive thermogenesis, and this paper tested that directly: "SNS activity and plasma leptin, ghrelin, and T3 and their changes with CR *were not related to AT." Its conclusion puts the driver elsewhere — "during early weight loss, AT is associated with a fall in insulin secretion and body fluid balance" — with AT becoming significant within 3 days and correlating with decreased insulin secretion at *r = 0.92, P < 0.001*[7]
- Key difference: Adrenaline and growth hormone not increased during chronic restriction[1]
- Calorie restriction causes skeletal muscle loss (−5% in 3-week study) along with fat loss[7]
- *The four-day figure traces to `caf01`, and the book bent it twice: `cif01` p.244 says four days of fasting increased total energy expenditure by 12%. The study is Zauner et al. 2000, held here in full — REE 3.97 → 4.43 kJ/min is +11.6%, and norepinephrine 1716 → 3728 pmol/L is +117.2%, matching the book's own 117 percent. Zauner measured RESTING energy expenditure — it is in the paper's title, and "total energy expenditure" appears in it zero times — and where the book reports insulin falling 17%, the paper reports "insulin did not change". Cite `caf01`, not the book. `caf02` (Webber) is in tension with it: resting metabolic rate was significantly raised at 36 h but no longer significantly above baseline at 72 h* (P = 0.06), and not significantly changed at all in men[1],[2],[3]
- Clinical outcome comparison, *in the review's own words: "superior decreases in body weight by CR vs IF/ADF regimens, yet comparable reductions in visceral fat mass, fasting insulin, and insulin resistance" — and two things it says that this file did not carry: a null, "None of the interventions produced clinically meaningful reductions in glucose concentrations," and its own limit, that these are "preliminary findings" and "more research is required before solid conclusions can be reached"*** — confirmed in six randomized IER-CER trials: IER equaled CER for weight loss in all, but two showed greater HOMA insulin resistance reductions with IER (−24% vs −4%, p=0.001) independent of body fat changes[8],[9]
- IF's benefits are *not solely* attributable to weight loss: in an isocaloric crossover trial, early time-restricted feeding improved insulin sensitivity, beta cell responsiveness, blood pressure and oxidative stress in men with prediabetes, with no significant weight change between arms[10]
- *That trial is eight men*, its authors' own words being that they demonstrate the effect "for the first time in humans" on "some aspects" of cardiometabolic health: twelve were enrolled to obtain eight completers, aged 56 ± 9, overweight and prediabetic, five weeks per arm. The record's own excerpts flag it — small sample, needs replication in a larger trial[10]