75 Hard Results: What Happens to Your Brain After 75 Days

75 Hard promises a mental transformation in 75 days: two workouts a day, a strict diet, no alcohol, a gallon of water, daily reading and a progress photo, with any slip sending you back to day one. Plenty of people finish it feeling proud and more disciplined. Plenty more burn out or restart several times. What does 75 days of strict rules actually do to your brain and habits, and what does the research say about the design?

What is 75 Hard?

75 Hard is a free programme created by American entrepreneur Andy Frisella, who describes it on his official 75 Hard page as a mental toughness programme rather than a fitness plan. As commonly described, the daily rules are:

• Two workouts of at least 45 minutes each, one of them outdoors. The official page says these can be as simple as two 45-minute walks.
• Follow a diet of your choice, with no cheat meals and no alcohol.
• Drink a gallon of water (about 3.8 litres).
• Read every day (usually described as 10 pages of a non-fiction book).
• Take a daily progress photo.

If you miss any task on any day, the official answer is simple: you start over on Day 1.

Is there any research on 75 Hard?

No peer-reviewed studies have tested the 75 Hard programme itself, as far as we could find. Claims about what it does to your brain come from personal accounts, not controlled research. What we can do is look at what research says about each ingredient: habit formation, all-or-nothing rules, training volume and hydration.

What actually happens to your brain after 75 days?

The most likely real change is not mystical. It is habit formation. Repeating actions daily in a consistent context makes them more automatic over time. A 2024 meta-analysis found median habit formation times of 59 to 66 days, with very wide individual variation from 4 to 335 days (Singh et al., Healthcare, 2024). So 75 days is long enough for some simple daily behaviours, such as a morning walk or reading before bed, to start feeling automatic for many people. More complex routines may take longer.

There is also a confidence effect that people often report: finishing something hard that you committed to publicly can change how you see yourself. That is plausible, but it is a personal experience rather than a measured outcome, and it depends on finishing.

What does the research say about each rule?

Is the restart-from-day-one rule helpful or harmful?

It is the most debated part of the programme. Supporters say it is the point: no negotiating, no modifying. The official page acknowledges critics who say the rule makes people feel like failures, and rejects that criticism.

The habit research points the other way on one specific question. In the UCL habit study summarised in the British Journal of General Practice, missing a single opportunity did not seriously impair habit formation. That means a restart rule is not needed to build habits. It may help some people commit, but for others it turns one bad day into a reason to stop altogether. If you want strictness without that trap, the two-day rule is a gentler alternative: miss once if you must, never twice.

Who should be careful with 75 Hard?

• Beginners to exercise, who may be better starting with one daily session and building up.
• Anyone with a history of disordered eating, as rigid diet rules and daily body photos can be harmful.
• People with heart, kidney or other medical conditions, especially regarding training volume and fluid intake. Check with a GP first.
• People who are pregnant or breastfeeding, who should get personalised advice.

This is general information, not medical advice.

How do you do 75 Hard (or a version of it) sensibly?

1. Make one workout easy. Treat the outdoor session as a walk. Keep intense training to one session a day, with recovery built in.
2. Choose a balanced diet, not a crash diet. Prioritise protein, vegetables and enough total energy to train. Our guide to how much protein you need per day is a starting point.
3. Drink to thirst and conditions. Use the healthdirect guide as a baseline, adding more for heat and exercise, rather than forcing a fixed volume.
4. Protect sleep. Two sessions a day plus work leaves little slack. If sleep drops, something else needs to give.
5. Decide in advance what happens after a slip. Restarting is the official rule. If you choose to continue instead, be honest that you are running a modified version.
6. Plan day 76. Pick the two or three habits you want to keep, at a sustainable level. The point is what remains after the challenge, not the challenge itself.

What lasts after 75 Hard?

The lasting value is the habits that survive. Research on self-control by Galla and Duckworth (2015) found that people with good self-control rely heavily on beneficial habits rather than constant effortful restraint. That is the realistic upside of a structured challenge: it can kick-start a few habits that then run with much less effort. For what drives that, see how long it takes to form a habit and why motivation fails. If you want a lower-intensity physical foundation, a daily walking habit built around a realistic step target may stick better than two forced workouts.