How Much to Eat on a 75-Day Challenge
Two 45-minute workouts a day change your calorie needs. Here's the TDEE math, a protein floor, a deficit ceiling, and a worked 185 lb example.
This article is general wellness information, not medical advice. Calorie and macro needs vary a lot between individuals, and nothing here is a prescription for you specifically. Talk to your doctor or a registered dietitian before starting an intense training program or a large calorie deficit.
The rules tell you to pick a diet. They never tell you how much of it to eat.
That gap is where most 75-day attempts quietly fall apart. You start strong, you eat “clean,” you train twice a day, and somewhere around day 18 the wheels come off. Flat workouts. Terrible sleep. A scale that stopped moving two weeks ago. Most people call that a discipline problem when the real culprit is arithmetic.
So here is the arithmetic. A five-step calculation you can run on yourself in about four minutes, a fully worked example at 185 lb, a protein floor, a deficit ceiling, and a plan for fuelling that second session.
Do you have to count calories on a 75-day challenge?
No. Half the people asking this think tracking is mandatory, so let’s settle it before the numbers.
75 Hard, the program created by entrepreneur Andy Frisella, requires a structured diet with zero cheat meals and zero alcohol. That’s the whole nutrition rule. It names no diet, sets no calorie target, and specifies no macros. Counting is one legal option among many, sitting alongside portion plates, whole-food rules, keto, and Mediterranean eating.
If you’re still deciding which framework to run, our 75 Hard diet plan guide walks through the four that hold up over 75 days. This article assumes you’ve picked one and now want the numbers behind it.
Skipping the count is fine; going in without a rough sense of what you actually need is what kills attempts. You can eat off a portion plate for 75 days and be perfectly compliant, but if that plate is 1,600 calories and you’re burning 600 extra a day in training, you’ll find out the hard way in week three.
Why two workouts a day change the math
Ninety minutes of training every day, no scheduled rest days, for 75 straight days.
But the internet wildly overstates what that costs. You’ll see people assume two workouts means 1,200 extra calories a day. Here’s what the sessions actually run, using Harvard Health’s 30-minute figures scaled to 45 minutes:
| 45-minute session | 125 lb | 155 lb | 185 lb |
|---|---|---|---|
| Walking, 3.5 mph | 161 | 200 | 239 |
| Weight lifting, general | 135 | 162 | 189 |
| Weight lifting, vigorous | 270 | 324 | 378 |
| Stationary cycling, moderate | 315 | 378 | 441 |
| Rowing, stationary, moderate | 315 | 378 | 441 |
| Elliptical, general | 405 | 486 | 567 |
A 45-minute walk and a 45-minute vigorous lift are not the same 45 minutes; the gap is roughly double. And for most people pairing one real session with one easier outdoor session, the daily add-on lands somewhere around 400 to 800 calories, not 1,200.
That number matters because it’s the amount you have to account for. How you account for it is where nearly everyone gets it wrong.
The five-step calculation
Step 1: Find your BMR
Mifflin-St Jeor is the standard. It was derived from indirect calorimetry in 498 healthy adults and published in the American Journal of Clinical Nutrition in 1990, with an R² of 0.71 against measured expenditure.
- Men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161
To convert: pounds ÷ 2.205 = kg, inches × 2.54 = cm.
Step 2: Pick one method, not both
This is the step that produces fantasy numbers. There are exactly two valid ways to get from BMR to a daily total, and you must choose.
Method A (recommended). Multiply BMR by a low activity multiplier that covers your non-exercise life only, then add the actual calories of both workouts from the table above.
Method B (faster, coarser). Multiply BMR by 1.9, the multiplier NASM defines as hard daily exercise or twice-a-day training, and add nothing.
| Multiplier | What it means |
|---|---|
| 1.2 | Sedentary: desk job, little movement outside training |
| 1.375 | Lightly active: on your feet some of the day |
| 1.55 | Moderately active: exercise 3 to 5 days/week |
| 1.725 | Very active: hard exercise 6 to 7 days/week |
| 1.9 | Extra active: physical job, or twice-a-day training |
The double-counting trap: never multiply by 1.725 or 1.9 and add your workouts on top. The high multipliers already contain your training. Do both and you’ll hand yourself a 4,000-calorie target, wonder why you’re gaining, and blame the program. If you’d rather skip the arithmetic entirely, the TDEE calculator handles steps 1 and 2 for you.
Step 3: Add both sessions (Method A only)
Look up each workout in the table, scale to your body weight, and add.
Step 4: Set a deficit, or don’t
That total is maintenance. Whether you subtract from it depends on your goal, and there’s a real ceiling on how much you should subtract. That gets its own section below.
Step 5: Split it into macros
Protein first, fat second, carbs fill the remainder. That gets its own section further down.
Worked example: 185 lb, 5’10”, 34 years old
185 lb is 83.9 kg and 5’10” is 177.8 cm. Both live in the Harvard table’s 185 lb column, so every number here is traceable rather than interpolated.
BMR: (10 × 83.9) + (6.25 × 177.8) - (5 × 34) + 5 = 1,785 calories
Say he works a desk job and trains with a vigorous 45-minute lift in the morning and a brisk 45-minute outdoor walk in the evening.
| Step | Calculation | Result |
|---|---|---|
| BMR | Mifflin-St Jeor | 1,785 |
| Method A base | 1,785 × 1.2 (sedentary) | 2,142 |
| AM session | Vigorous lifting, 45 min | +378 |
| PM session | Walking 3.5 mph, 45 min | +239 |
| Method A maintenance | ~2,760 | |
| Method B maintenance | 1,785 × 1.9 | ~3,390 |
Those two numbers are 630 calories apart, and the honest answer is that Method B runs high for him. The 1.9 multiplier assumes a physical job or athlete-grade twice-a-day training, and a desk worker doing one lift and one walk is neither.
Swap in harder sessions and a more active baseline and the gap closes. At 1.375 with a vigorous lift plus 45 minutes of moderate rowing, Method A gives about 3,270, which is close to Method B’s 3,390. That’s the rule of thumb: Method B is only accurate if both sessions are genuinely hard and you move a lot outside them. Otherwise trust Method A and take the lower number.
So his maintenance is roughly 2,760. Now the deficit.
Your deficit ceiling: how big is too big
The CDC puts sustainable loss at 1 to 2 lb per week, the rate people are most likely to keep off. The ISSN’s position stand on diets and body composition sharpens that: a weekly reduction of 0.7% of body weight outperformed 1.4% for preserving lean mass, and the higher your baseline fat mass, the more aggressively you can cut.
The working rule: lose 0.5 to 1.0% of body weight per week, biased to the low end if you’re already lean or if both sessions are intense.
For our 185 lb example, 0.5% is 0.93 lb per week, or roughly a 460-calorie daily deficit. That puts him at about 2,300 calories. At the aggressive 1.0% end he’d be near 1,840, and that’s where things get risky.
The 2023 IOC consensus statement on Relative Energy Deficiency in Sport describes low energy availability on a spectrum, from adaptable to problematic, with under 30 kcal per kg of fat-free mass per day as the commonly used research cut-off. Energy availability is what’s left after training, divided by lean mass.
Run it for our example, assuming 18% body fat (an assumption, so treat it as a rough estimate, and the body fat calculator will get you closer):
- Fat-free mass: about 69 kg
- At maintenance, 2,760: (2,760 - 617) ÷ 69 = about 31 kcal/kg FFM
- At a 0.5% deficit, 2,300: (2,300 - 617) ÷ 69 = about 24 kcal/kg FFM
Two-a-days leave you barely above the cut-off at maintenance. Any meaningful deficit takes you below it.
Those thresholds come from athlete research and the 2023 statement is explicit that low energy availability is a spectrum rather than a switch, so being under 30 for a stretch is not a diagnosis. But it does explain week three better than any lecture about willpower. The tells are specific: wrecked sleep, a flat mood, a resting heart rate that drifts, lifts that stall, a libido that vanishes, and sessions you start skipping.
The practical version: run the shallow end of the range, expect a slower scale than the before-and-afters suggest, and treat maintenance as a completely legitimate choice for 75 days. Plenty of people finish and change shape without a deficit at all. Our guide to how much weight you actually lose sets realistic expectations, the weight loss timeline calculator shows how long your target rate takes, and the calorie deficit calculator will run your own numbers in a few seconds.
Protein, carbs, and fat: how to split it
Protein comes first
The ISSN protein position stand puts 1.4 to 2.0 g/kg/day as sufficient for most exercising individuals. Morton’s 2018 meta-regression of 49 studies and 1,863 participants found the resistance-training dose response plateaus near 1.62 g/kg/day, which makes a clean practical floor.
If you’re in a deficit while lifting, ISSN notes 2.3 to 3.1 g/kg may be needed to maximise retention of lean body mass, though that upper band is aimed at lean, trained people. The 1.6 to 2.2 g/kg range most coaches use sits comfortably inside all of it.
For our 185 lb example that’s roughly 136 g at the floor and 151 g at 1.8 g/kg. Distribution matters too: ISSN suggests 0.25 g/kg per meal, or 20 to 40 g absolute, every three to four hours. Around 21 g per meal is his minimum, so four or five meals of 30 to 40 g clears the bar comfortably. The protein intake calculator gives you the number in grams.
Carbs and fat fill the rest
The ISSN nutrient timing stand cites 5 to 12 g/kg/day of carbohydrate for athletes, with 8 to 10 g/kg reserved for those training at moderate to high intensities.
Now notice the tension. For our example, even the bottom of that range is 420 g of carbs, which is 1,680 calories on its own. Add 150 g of protein and you’ve spent 2,280 of a 2,300-calorie target with nothing left for fat. The athlete carb range assumes eating at or above maintenance. In a deficit you will sit below it, and that’s the trade-off you’re making.
One workable split at 2,300 calories:
| Macro | Grams | Calories |
|---|---|---|
| Protein | 150 | 600 |
| Carbohydrate | 280 | 1,120 |
| Fat | 65 | 585 |
That’s one example, not a prescription. The principle behind it is the part to keep: set protein, then give fat a floor you refuse to dip under, then let carbs flex. Fat is the macro people accidentally squeeze to nothing when they treat it as the leftover, and hormones don’t appreciate it. The macro calculator will split your own target into grams.
Fuelling the second workout
Every article treats two-a-days as a scheduling problem. It’s a fuelling problem too, and the second session is where it shows.
That session usually lands six to ten hours after the first, often after a full workday, often on a tank you never refilled. ISSN’s nutrient timing guidance is direct about this: ingest 0.6 to 1.0 g of carbohydrate per kg of body mass within the first 30 minutes after a glycogen-depleting bout, then again every two hours for the next four to six hours. For our 185 lb example, that’s 50 to 84 g of carbs in that first post-workout window.
A simple three-slot day:
- Post-AM refuel: 50 to 80 g carbs plus 30 to 40 g protein. Rice, oats, fruit, potatoes, and a protein source. This is the meal people skip.
- Pre-PM top-up: 30 to 60 g carbs, 60 to 90 minutes out. Low fat, low fibre, easy to digest.
- Post-PM protein: 30 to 40 g protein with whatever carbs are left in your target.
One wrinkle if your outdoor session is the second one. In hot weather, sweat losses stack on top of everything else, and dehydration will read as fatigue long before your fuelling does. The sweat rate calculator gives you a replacement number, and our supplements guide covers electrolytes without the marketing. For the scheduling half of the problem, see the two-a-day workout schedule guide.
How to know it’s working
Judge your target on a two-week rolling average of morning weight, never a single reading. Daily weight swings on water, sodium, and glycogen, all of which move a lot when you’re training this much.
When you’re fine-tuning the rate, adjust by 100 to 200 calories, not 500. And weigh the trend against progress photos and measurements, because recomposition routinely hides real fat loss behind a flat scale.
That’s also the case for logging it somewhere consistent. Reset75 tracks a weigh-in as a measurement task alongside the rest of your daily checklist and charts the trend for you, so the two-week average is just there instead of being a spreadsheet chore. If you only want the number, the weight tracker does the same job in your browser.
We make a tracker, not a diet product. There’s no macro coaching to upsell you, which is exactly why we can just publish the arithmetic.
Run your own numbers in the calorie deficit calculator, get the plan on paper with our meal prep guide, and then go eat enough to finish.
Frequently Asked Questions
How many calories should I eat on a 75-day challenge?
There is no prescribed number, because the program names no diet and no calorie target. Calculate your BMR with Mifflin-St Jeor, then either multiply by 1.9 (the twice-a-day training multiplier) or multiply by 1.2 to 1.375 and add both workouts separately. Most people land 400 to 800 calories above their pre-challenge maintenance. Never do both adjustments at once.
Do you have to count calories on a 75-day challenge?
No. 75 Hard, created by Andy Frisella, requires a structured diet with zero cheat meals and zero alcohol, but it names no diet and requires no tracking. Counting is one legal option alongside portion plates, whole-food rules, keto, or Mediterranean. You don't have to count, but you should know roughly what two workouts a day cost you.
How much protein do you need with two workouts a day?
The ISSN position stand puts 1.4 to 2.0 g per kg of body weight per day as sufficient for most exercising people, and Morton's 2018 meta-regression found gains plateau near 1.62 g/kg. If you're also in a calorie deficit while lifting, ISSN says 2.3 to 3.1 g/kg may be needed to protect lean mass. Spread it over four or five meals of 20 to 40 g.
Should I eat at maintenance or in a deficit during a 75-day challenge?
Both work. The deficit is just harder to sustain across 75 days of two-a-days. If fat loss is the goal, cap the deficit at roughly 0.5 to 1.0% of body weight per week. If performance, muscle, or simply finishing is the goal, maintenance is a legitimate choice, and plenty of people finish and change composition without a deficit at all.
Why am I so tired in week three of a 75-day challenge?
Usually under-fuelling, not weak willpower. Two 45-minute sessions a day with no rest days plus an aggressive deficit pushes energy availability low, and the IOC's 2023 REDs consensus links that to poor sleep, mood changes, and dropping training performance. Add 200 to 300 calories, mostly carbohydrate around your workouts, and reassess after two weeks.
Can I eat back the calories I burn in my workouts?
Yes, if you built your target from a low activity multiplier and are adding workouts on top. No, if you already used the 1.9 twice-a-day multiplier. That number already includes both sessions, so eating them back a second time doubles the count and erases your deficit.
How big should my calorie deficit be with two workouts a day?
Aim for 0.5 to 1.0% of body weight lost per week, biased to the low end. The ISSN's review found losing 0.7% of body weight per week preserved lean mass better than 1.4%, and the CDC puts sustainable loss at 1 to 2 lb per week. The leaner you already are, the smaller the deficit should be.
What should I eat between my two workouts?
Carbohydrate, mainly. The ISSN nutrient timing stand recommends 0.6 to 1.0 g of carbohydrate per kg of body mass within 30 minutes of a glycogen-depleting session, repeated every two hours, when a second session is coming the same day. Add 20 to 40 g of protein to that meal and you've covered both recovery and the next workout.