These Doctors Were Wrong About Fasting... and Why I Strongly Disagree

DeLauer positions resistance training as the missing element in the anti‑fasting narrative. He points out that both Attia and Patrick lost muscle not because of fasting per se but because they did not combine it with an adequate muscle stimulus. When muscles are loaded, the body maintains them even during calorie restriction. This is supported by the research from Mike Ormsbee showing that resistance training on fasting days not only protects muscle but also triggers a sustained increase in fat oxidation—potentially more beneficial than the acute fat burn of cardio. He stresses that the anabolic window is wide enough that post‑workout nutrition can be delayed, so one can train fasted and eat later without compromising the response.

DeLauer acknowledges that fasted cardio was once a cornerstone of his approach. He now sees it as a mistake because it creates a calorie deficit that includes muscle protein alongside fat. He references research indicating that the fat loss from fasted cardio is unlikely to offset the muscle loss. Meanwhile, the signalling benefit of resistance training—both for muscle preservation and prolonged fat oxidation—makes it the superior choice during fasting. He frames this as a course correction for anyone following his older material.

DeLauer counters the concern that skipping a meal means permanently losing a protein opportunity. He explains that the body does not rigidly reset every 24 hours; it can compensate over longer periods. He points to literature demonstrating that even 100+ grams of protein in one meal is not wasted or converted to fat but is gradually released. Coupled with the 24–48‑hour synthesis window, this means a person can fast for 20 hours, train, then eat a large, protein-rich meal and still support muscle maintenance or growth.

DeLauer differentiates between the moderate intermittent fasts he recommends and the extended fasts that Attia and Patrick previously practiced. Attia’s quarterly 7–10‑day water fasts, for example, resulted in a cumulative 10‑pound lean mass loss over 3 years. DeLauer agrees that such prolonged fasts are detrimental to muscle. However, he contends that a 16–22‑hour fast, especially with resistance training, lies on a safe part of the curve. He draws on the principle that sufficient mechanical stimulus offsets the mild deprivation, making the practice viable for body composition and metabolic health.

For many years DeLauer believed that doing cardio while fasting maximised fat burning. He now admits this view was narrow, focused only on fat loss and not muscle preservation. Research from Ormsbee’s lab suggests that fasted cardio indeed burns fat acutely but does not send the muscle-preserving stimulus of resistance training. Moreover, the net equation of fat lost versus muscle lost makes fasted cardio a poor choice for anyone concerned with lean mass. He explains that the 'afterburn' (EPOC) after cardio is less significant than the signaling change triggered by resistance training, which leads to greater fat oxidation throughout the rest of the day. This recognition forced him to completely pivot on what he recommends during fasting days.

DeLauer describes a nuanced finding from Ormsbee’s lab that goes beyond the well-known EPOC. While intense exercise of any kind can increase post-workout calorie burn, the lab found that resistance training specifically activates a signalling cascade that instructs the body to oxidise a greater percentage of fat throughout the remainder of the day. This is not merely an elevated metabolic rate; it is a shift in substrate utilisation. Thus, even though a bout of fasted cardio might burn more fat in the immediate moment, resistance training yields a sustained, signal-driven fat oxidation that could be more valuable during a fast.

DeLauer argues that the body does not operate on a strict 24‑hour clock for calories or protein. While eating multiple small meals is common, the physiological reality is that a large bolus of protein can be absorbed slowly, with amino acids released over many hours. Combined with the fact that muscle protein synthesis stays elevated for 24 to 48 hours after resistance training, this means that a person can fast, train, then consume their daily protein target in a compressed window without compromising muscle repair. He emphasises that the body treats total intake over longer periods, not necessarily within a single day, so compensating with more food on other days can offset the deficit.

DeLauer acknowledges that Peter Attia and Rhonda Patrick changed their minds on fasting mainly because of lean mass loss. Attia reported losing 10 pounds of muscle over 3 years of extended fasts; Patrick noted she wasn’t making up protein when skipping meals. DeLauer counters that the variable missing from their experiences was adequate resistance training. He invokes Dr. Don Layman’s principle that 60–70% of muscle maintenance comes from the stimulus itself. When humans fast without using muscles, the body sees no reason to keep metabolically expensive tissue. If muscles are regularly challenged with resistance, however, the body preferentially preserves them because they are interpreted as necessary for survival. Therefore, the problem is not fasting but the lack of stimulus during fasting. He further supports this by noting that protein synthesis can be delayed and large protein meals can still meet needs.