What to Eat After Fasting on Your Period: What the Research Shows

What to Eat After Fasting on Your Period: What the Research Shows

A small study of 11 adults, six of them women, tested what happens after a full day without food. People did not eat back all the calories they skipped. They only replaced about six in ten. After the fast, they naturally chose more fat and protein, and fewer carbs. The study did not look at the period on its own, but its findings can guide what you eat after any fast.

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

The Short Version

• What they tested: How hungry people feel during a 24-hour fast, and what they eat afterward.
• Who did it: Grant Tinsley at Texas Tech University, published in Physiology & Behavior in 2018.
• How many people: 11 adults, 6 of them women. Exact ages are not stated in the abstract.
• How long: Each person fasted for 24 hours, twice, so results could be checked against each other.
• What happened: People replaced only about 6 out of 10 calories after the fast, and ate more fat and protein.
• Read the study yourself: Physiology & Behavior 2018 →

What They Wanted to Find Out

Many women wonder what to eat once a fast ends, especially around their period. Researchers wanted to know what happens to hunger during a full day without food. They also wanted to see what people eat once they finally sit down to a meal. This matters because what you eat after fasting can affect how your body feels for the rest of the day, something also explored in this study on fasting and PMS mood.

The researchers did not design this study around the period or the menstrual cycle. They simply asked healthy adults to fast for 24 hours, twice, and tracked their hunger hour by hour. Then they watched what people chose to eat once the fast was over. Their aim was to see whether hunger patterns and after-fast eating were steady and predictable.

Who Was in the Study

Who they were: The abstract does not give exact ages or weight categories. It describes them only as healthy adult volunteers, 6 women and 5 men.

What the fasting actually looked like: Each person fasted for a full 24 hours, with no food at all. In the last 8 hours of each fast, they were watched closely. Every hour, they rated how hungry they felt, how full they felt, and how much they wanted to eat. After each fast, they were allowed to eat as much as they wanted.

What Happened

The biggest finding: people did not make up for the missed food. On average, they only ate back about 6 out of 10 of the calories they had skipped.

• People's hunger ratings changed a lot from person to person, more so than their fullness ratings.
• How reliable each hunger rating was depended on what was being measured, with fullness the steadiest.
• People who carried more body fat tended to report feeling hungrier and wanting food more.
• How much a person ate back after the fast was linked to how hungry they felt during it.
• Body fat level did not predict how much food a person ate back afterward.

What Did Not Change

• The study did not measure muscle loss or muscle gain at all.
• Body fat percentage itself did not shift during this short study.
• The study did not track blood sugar changes over time, only eating behavior.

What the Researchers Said

The researchers concluded that people naturally shift toward more fat and protein, and fewer carbs, after a fast. They also said a "test fast" like this could help identify who is likely to cope well with regular fasting.

What This Means for You

• Do not expect to "make up" all the food you missed. In this study, people only replaced about 6 out of 10 calories.
• Your first meal after fasting may naturally lean toward fat and protein. This was true for both the women and men in the study.
• For women specifically: this study cannot say whether period timing changes hunger or eating after a fast — it was not studied here.
• If you fast on your period, choosing protein-rich or iron-rich foods afterward is common guidance, though this particular study did not test iron or period symptoms directly. You can read more in this study on fasting and iron levels in women.
• Hunger swings a lot between people. Do not worry if your hunger during a fast feels stronger or weaker than someone else's.
• If mood around your period is a concern, this study on fasting and PMS may be useful reading too.

What This Study Could Not Tell Us

• Only 11 people took part, so the findings are not certain to apply to everyone.
• Only 6 of the 11 people were women, which limits what we can say about women specifically.
• The abstract does not say whether any of the women were tracking their period during the study.
• It ran for just two 24-hour fasts, so it cannot say what happens with regular, repeated fasting.
• Eating amounts were self-reported by people eating freely, not measured in a lab setting.
• Funding for this study is not reported in the abstract.

The Study Details

Tinsley, G. M., Moore, M. L., & Graybeal, A. J. (2018). Reliability of hunger-related assessments during 24-hour fasts and their relationship to body composition and subsequent energy compensation. Physiology & Behavior. PMID: 29438660

Common Questions

What should I eat right after fasting on my period?

This study did not test period timing directly. It found that, in general, people naturally lean toward more fat and protein after a fast, and less carbs.

Will I overeat after a fast because of hunger?

Not necessarily. In this study, people only replaced about 6 out of 10 missed calories on average, so most people did not overeat.

Does hunger during a fast affect how much I eat afterward?

Yes. People who reported wanting food more during the fast tended to eat more afterward, according to this study.

Does body fat level change how hungry you get while fasting?

In this small study, people who carried more body fat reported feeling hungrier and more drawn to food during the fast.

Did this study look at women's hormones or the menstrual cycle?

No. The study tracked hunger and eating in 11 adults, 6 of them women, but did not study hormones or period timing.

More Research Like This

• Alternate-Day Fasting Improved Premenstrual Mood in Overweight Women
• Two-Day Fasting Cycles Lowered Iron in Healthy Women
• 5:2 Fasting Improved Menstrual Regularity in Women With PCOS
• Does Time-Restricted Eating Change Women's Hormones?
• Intermittent Fasting and Ovarian Reserve in Women
• Intermittent Fasting Increases Telomere Length in Young Women
• Early Time-Restricted Eating for Fat Loss in Women

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