75 Hard: What the Science Says About the Internet's Most Intense Challenge
Table of Contents
Few fitness challenges inspire as much devotion - and as much debate - as 75 Hard. The hashtag has racked up over a billion views, and its creator says more than a million people have attempted it. It's intense, uncompromising, and for some people genuinely transformative.
It's also the challenge experts have the most to say about. So let's do what we always do: credit what's genuinely good about it, and be honest about where the science pushes back. Because with 75 Hard, the two are tangled together.
What 75 Hard actually is
Created in 2019 by entrepreneur Andy Frisella, 75 Hard is a set of daily rules you follow for 75 straight days: two 45-minute workouts a day (one must be outdoors); follow a strict diet of your choice with no alcohol and no cheat meals; drink a gallon of water; read 10 pages of a nonfiction or self-improvement book; and take a daily progress photo. Miss any part of any rule, and you start over at day 1.
Frisella is refreshingly clear about one thing: he doesn't call it a fitness program. He calls it a mental-toughness program - an 'Ironman for your brain.' That framing matters, because it's the key to understanding both its appeal and its problems. (A huge online community, r/75Hard, documents the highs and lows in real time.)
What's genuinely good about it
Let's give credit where it's due. The individual habits 75 Hard bundles together are, on their own, well supported: regular exercise, staying hydrated, reading daily, cutting out alcohol, and following a structured routine are all good for you. Stacking several healthy behaviours and repeating them daily is a legitimately powerful way to build momentum.
There's also real psychological value in setting a hard, sustained goal and following through. Completing something difficult can build genuine self-confidence and prove to yourself that you can commit. Plenty of people finish 75 Hard feeling accomplished and more disciplined - and that's not nothing.
Where the science pushes back
Here's the honest part. Several of 75 Hard's specific rules aren't evidence-based, and some experts actively worry about them. The Cleveland Clinic points out there's little scientific evidence behind the approach, and that its most rigid rules can do more harm than good.
The no-rest-days rule is the biggest problem. Two workouts a day for 75 straight days, with zero scheduled recovery, runs against a basic principle of exercise science: your body doesn't get fitter during exercise - it gets fitter while recovering from it. Training hard every single day without rest is a recipe for overuse injuries, deep fatigue and burnout, not peak fitness. This alone is why many sports scientists advise against following the rules literally.
The restart rule versus how habits actually form
The 'miss one thing and start over at day 1' rule is the part that most contradicts the science of behaviour change. A well-known University College London study that tracked how habits actually form found something reassuring: missing a single day did not meaningfully derail the habit-building process. One slip simply doesn't matter much in the long run.
75 Hard treats one missed page of reading or one indoor-only workout as total failure requiring a complete restart. Psychologically, that's backwards. Real resilience isn't never missing - it's bouncing back after you do. An all-or-nothing framework can turn a minor, normal slip into a sense of failure, which for many people is discouraging rather than motivating.
Want the honest, evidence-based take on fitness trends? Get new breakdowns like this one delivered to your inbox.
A note on the diet, the photos, and your wellbeing
Two of the rules deserve a gentle, honest word. The rigid 'no cheat meals ever' diet and the mandatory daily progress photo work fine for some people - but clinicians caution they can be a real risk for others. For anyone with a history of disordered eating or a difficult relationship with food or their body, a strict, unforgiving diet plus daily body-check photos can reinforce unhealthy patterns.
If that's you, please approach this one with care, and consider talking to a doctor or a qualified professional before starting. A challenge is supposed to make your life better, not become a source of shame or obsession - there's no toughness prize worth your mental health.
(One practical note too: the fixed 'gallon of water a day' rule isn't individualised either. For most healthy adults, spread across an active day, it's fine - but water needs vary with your size, climate and activity, and more isn't automatically better.)
A smarter way to get the benefits
Here's the encouraging conclusion: you can capture almost everything good about 75 Hard - daily movement, better habits, structure, follow-through - without the rules experts flag. Build a challenge that includes rest days, allows sensible flexibility, and treats a missed day as a reason to continue, not restart.
This is really just good habit design, and it's exactly what the science of streaks and tracking supports: consistency over perfection. If you want intense-but-sustainable daily movement, something like interval walking or a structured training block gives you the discipline and the daily win without grinding yourself into the ground.
The verdict
75 Hard is a fascinating mix: a bundle of genuinely healthy habits wrapped in some genuinely questionable rules. The discipline it demands is real, and for the right person at the right time it can be a powerful reset. But the no-rest, no-flexibility, restart-on-any-miss structure isn't backed by science, and for some people it carries real risks. Take the spirit - commitment, consistency, daily effort - and build a version that's as smart as it is hard.
*Harder is a social challenge platform where you set challenges, submit daily proof, and build a public track record of doing hard things - the sustainable way, with consistency that lasts a lot longer than 75 days.*