Buff daddy: Dwayne Johnson and Zac Efron in the movie reboot of Baywatch. Credit:Frank Masi/Paramount Pictures But unlike bodybuilders, who get to walk off stage and dive straight into a pile of donuts, action stars are expected to maintain this fragile state through training and pre-production right through the gruelling production period. It's one thing to shred when all you have to do is work out for a few hours and then let your body rest; it's quite another to endure a 16-hour location shoot and 4am starts when all you're allowed to eat is poached tilapia with some steamed broccoli. For me, it's not that, as E. Alex Jung suggested in a similarly concerned Vulture piece, Efron is "too swoll" - in fact, as far as Hollywood action bodies go, Efron hasn't (yet) entered the arena of extreme size that his co-star Dwayne "The Rock" Johnson or Guardians Of The Galaxy's Dave Bautista have inhabited for some time. Rather, it's that he looks so shredded. (Shredding, ripping or cutting, for those not regularly lurking bodybuilding.com forums, is the process of shedding body fat while maintaining muscle size and tone until the muscles "pop" from beneath the skin. Bodybuilders typically only do this once a year for 12 or so weeks pre-competition. Read too much about it and you may want to recover with a nice calming shreds video.)

Zac Efron, left and Robert De Niro in Dirty Grandpa. Efron's presence in the film made the lithe-yet-buxom bodies of his female co-stars look positively normal by comparison. This, in 2017, is the norm for male superstars: it's no longer enough to be jacked, now they have to be cut as well. Hugeness has given way to leanness. It may be tempting to sniff at this develpment. Like, hooray, male stars are finally experiencing the hell their female counterparts have known for many years! Chris Pratt looking more "ripped" than "shredded" in a scene from 'Guardians Of The Galaxy'. Credit:Disney - Marvel But this nightmare of extreme aesthetics is no win for gender equality. As Jung writes, "It's as though the lesson we learned from feminism was to apply similarly rigorous body standards to men, instead of examining why we applied them to women in the first place. Everybody loses!"

This baseline level of aesthetic shred goes beyond the extreme body transformations that method actors like Christian Bale and Jared Leto have long prided themselves on. Indeed, as Angelica Jade Bastien wrote for The Atlantic late last year, "method acting" has become a measure of machismo: "method acting, as it's practiced today, depends on framing less drastic techniques as feminine, and therefore inferior." Linda Hamilton in a scene from the movie Terminator 2. (It says something that the most revered body transformation of any actress, Linda Hamilton's Terminator 2 makeover – despite the film's crucial feminist themes – is coded by commentators in masculine terms: her jacked shoulders, her impressive and functional fitness, and the fact she could pump-load a 12-gauge shotgun with one hand. Other method actresses are, as Bastien notes, simply praised for being brave enough to "go ugly".) But Efron and his peers are not "method acting" as hot studs. As some critics have noted, his body in Baywatch is not the supple, broad-shouldered form of an Olympic swimmer's, despite the fact his character is a two-time gold medallist. Rather, it's the end result of an expectation of extreme male hotness regardless of the role or context. For an insight into the reality of what it takes to achieve this body, just follow Chris Pratt on Instagram. His #whatsmysnack videos have become an increasingly bleak series of missives from the land of 5 per cent bodyfat as he reveals the "meals" he has to eat each day to stay shredded enough to believably portray a Velociraptor trainer. The video about his cucumber rolls was like an Ingmar Bergman short:

The formerly husky Parks & Recreation sweetheart began his transformation when cast as a member of Seal Team 6 in Zero Dark Thirty back in 2012, unveiling his very un-Andy-Dwyer body in a selfie that sent shockwaves of thirst around the galaxy. Since then, he's become an in-demand action stud, with the diet and training regime to go with it. Pratt and Efron's gruelling workouts and sorrowful, dehydrated eye-bags are typical of the modern action superstar. Hell, Baywatch isn't even an action movie – now even comedy stars are expected to be cut. Efron is one of the most delightful comic presences on screens (go watch 17 Again again), so why does he need to look like he's about to show the judges his front lateral spread?

Johnson praised his younger co-star's approach to the Baywatch shoot without a shred of irony: "Athletes know how hard it is to prep, train, and diet for a competition. It's months of focused sacrifice all leading up to one particular event that takes place in one night. "In the case of Baywatch," he added, "Zac's had to apply the diet and training strategy of an elite athlete, but he's also had the 'added bonus' of needing to maintain that look for months while we're shooting." Dwayne, my dude, that is not actually a good thing. Perhaps it's the commie in me, but it's time the unions and guilds draw a line in the sand, as far as the studios' duty of care for their stars – both male and female – is concerned. Orlando Bloom recently revealed, to gales of laughter, that one of his intense workouts nearly, well, killed him. What the actual hell on earth? It may be boring to suggest it in the multi-million-dollar world of late-capitalist blockbuster moviemaking, but it's not fair or ethical to expect stars to maintain these physiques year round. (Then again, what's that joke about ethics in capitalism? "'Ethical capitalism' isn't"?)

This race to the bottom (of the fat ratio) was first chronicled by reporter Logan Hill, whose 2014 Men's Journal essay, 'Building A Bigger Action Hero', is essential, sobering reading. "Maintaining extremely low body fat for the duration of a multimonth shoot is nearly impossible and often dangerous: The stress can make an actor ill, damage internal organs, and make him susceptible to other injuries," Hill wrote. "Even in the best-case scenario, calorie deprivation can exhaust an actor, making him light-headed, distracted, and fatigued." It reminds me of the nightmarish preparation process the Victoria's Secret models endure, which in turn is very similar to physique bodybuilders' pre-comp regimes. But when even bodybuilders themselves have begun to wonder if the sport has gone too far (compare the golden era of Arnie and Franco to the mindboggling hugeness of Generation Iron 2), it may be worth stepping back and asking ourselves what madness we have descended into when an extreme shred is considered standard practice for simply appearing on screen.

And Zac, if you're reading, consider this a standing invitation to come eat some high-sodium food court stir-fry and non-complex carbs sometime.