How to Eat Through Your Menstrual Cycle: A Phase-by-Phase Guide With Real Numbers

A practical phase-by-phase guide to eating with your cycle: calories, protein and iron targets, what actually helps PMS, and when to see a doctor.

Your cycle changes your appetite, your energy expenditure and how hard training feels — every month, whether you track it or not. Rather than fighting that with willpower, it is simpler to make two or three specific adjustments per phase. Here is what actually changes, by how much, and what to do about it.

What actually changes across the cycle

Day 1 is the first day of bleeding. The follicular phase runs from there to ovulation (around day 14 in an average cycle), and the luteal phase runs from ovulation to your next period — that one is fairly fixed at 12 to 14 days. A normal cycle is 21 to 35 days long, and a few days of month-to-month variation is fine.

Measurable differences in the luteal phase compared to the follicular phase:

resting energy expenditure is 2–8% higher, which for most women is 80–250 kcal per day
core temperature is 0.3–0.5 °C higher, so hard sessions feel harder, especially in summer
spontaneous food intake rises by 90–280 kcal per day — that is a hormonal signal, not weak discipline
water retention of 0.5–2 kg in the last 3–6 days before your period

Follicular phase (days 1–14): use it for the heavy work

Energy is steadier, recovery is faster, and strength peaks here for most women. Schedule your heaviest loading now — for example 4–5 sets of 3–6 reps on squats and deadlifts.

Carbs around training: a meal with 1–1.5 g/kg of carbs 2–3 hours before, plus 30–60 g of easily digested carbs 30–60 minutes before a hard session.
Protein: 1.6–2.2 g/kg of body weight per day, spread over 4 meals of 25–40 g each. For a 65 kg woman that is roughly 105–140 g per day.
Calories: if you are building, a surplus of 150–250 kcal is easiest to hold here; if you are cutting, a 300–500 kcal deficit is most tolerable in this phase.

Your period: iron is the one nutrient worth tracking

Average blood loss per cycle is 30–50 ml, which works out to about 0.5–1 mg of iron per day more than men need. That is why the recommended intake for women of reproductive age is 18 mg per day versus 8 mg for men.

Heme iron (15–35% absorbed): 100 g beef ≈ 2.5–3 mg, 100 g liver ≈ 6–9 mg, 100 g dark chicken meat ≈ 1 mg.
Non-heme iron (2–10% absorbed): 100 g cooked lentils ≈ 3.3 mg, 100 g cooked spinach ≈ 3.6 mg, 100 g chickpeas ≈ 2.9 mg.
Vitamin C with the meal raises non-heme absorption 2–3 fold. 50–100 mg is enough — half a red pepper or one kiwi.
Coffee and black tea with a meal cut iron absorption by up to 50–60%. Move your coffee at least an hour away from your main meat or legume meal.

Do not take an iron supplement just in case — excess iron accumulates and causes its own problems. Get bloodwork first: a full blood count and ferritin.

Luteal phase (days 15–28): you burn more, so eat more

Most mistakes here come from treating hunger as the enemy. It works better to add the 100–250 kcal you are already burning, on purpose and on schedule.

Add one planned snack of roughly 30 g protein + 40 g carbs — for example 200 g of Greek yoghurt with 40 g of oats and fruit.
Push protein to the top of the range, 2.0–2.2 g/kg, since progesterone slightly increases protein breakdown.
Do not slash carbs; 3–5 g/kg per day keeps training quality and mood stable.
Drink 2.5–3 litres of water a day and do not cut salt — salt restriction usually makes bloating feel worse, not better.

Sugar cravings

Banning sweets backfires. What works: eat 20–30 g of protein and 8–10 g of fibre before you reach for something sweet, and build in a planned 150–250 kcal dessert daily. Sleep matters too — under 6 hours measurably raises hunger the next day, so aim for 7–9 hours.

PMS: what the numbers support

Calcium 1000–1200 mg per day has the strongest evidence for reducing PMS symptoms. Three dairy servings (200 ml milk + 150 g yoghurt + 40 g cheese) gets you to roughly 900–1000 mg.
Magnesium 200–360 mg per day helps with cramps and bloating in a subset of women.
Omega-3, 1–2 g EPA+DHA per day — two 100–150 g servings of oily fish per week — reduces period pain intensity.
Keep caffeine under 200–300 mg (one espresso ≈ 60–80 mg) and alcohol minimal in the final week; both worsen sleep and irritability.
Fibre 25–30 g per day keeps digestion steady, since progesterone slows gut transit.

Bloating and the scale

A 0.5–2 kg rise before your period is water, not fat, and it clears within 3–6 days. So do not judge progress from one morning: use a 7-day rolling average, or compare the same phase month to month. Cutting calories further because of that spike is the most common way to wreck an otherwise good plan.

If your period has stopped

In women who train, the usual cause is low energy availability — under 30 kcal per kg of fat-free mass per day after subtracting what you burn in training. For a 60 kg woman at 20% body fat (48 kg fat-free mass), that threshold is about 1450 kcal left over after exercise. A missing period is not a sign of being in shape; it is your body shutting functions down, with bone density loss that is hard to get back.

When to see a doctor

Bleeding longer than 7 days, or soaking through a pad or tampon every hour for 2 hours in a row.
Cycles consistently shorter than 21 days or longer than 35 days, or no period for 3 months or more when you are not pregnant.
Pain that standard painkillers do not touch and that costs you a working day — endometriosis and fibroids need to be ruled out.
Fatigue, breathlessness on light effort, pallor, palpitations or hair loss — ask for a full blood count and ferritin to check for anaemia.
Mood changes that wreck your work and relationships every month (possible PMDD) — that is treatable, not something to endure.

This is general information, not a substitute for a consultation. If you use hormonal contraception, the phases are much flatter and most of these adjustments do not apply — keep intake steady across the month instead.

The short version

Protein 1.6–2.2 g/kg year-round; go to the top of the range in the second half of your cycle.
In the luteal phase, deliberately add 100–250 kcal instead of fighting the hunger.
Iron 18 mg per day, paired with vitamin C and kept an hour away from coffee; supplement only after a ferritin test.
Calcium 1000–1200 mg, magnesium 200–360 mg and two oily fish servings a week are your best moves against PMS.
A 0.5–2 kg pre-period jump on the scale is water — track the weekly average and leave your plan alone.