How to Refeed After a Fast (16–72+ Hours)

Quick answer: To refeed after a fast, start with a small, easy-to-digest meal that includes a clear protein source. Then increase portions gradually and keep the first few meals simple—especially after longer fasts.

Refeeding after a fast is just a fancy way of saying: don’t go from “zero” to “all-you-can-eat buffet” in one bite.

People fast for a bunch of reasons—fat loss, appetite control, or broader metabolic health goals. But results can vary, and expert guidance typically emphasizes that what and how much you eat still matters (not just the eating window) (NIH MedlinePlus, 2020).

Refeeding is how you keep the benefits you’re after… and avoid the classic post-fast problems like bloating, cramping, “why is my stomach doing this,” or a big energy crash.

---

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Talk with a healthcare professional before fasting or refeeding—especially if you’re pregnant, have diabetes, kidney/heart disease, a history of eating disorders, or you’ve had very low intake for multiple days.

First: when is refeeding actually dangerous?

For most healthy adults doing intermittent fasting or an occasional 24-hour fast, refeeding is mainly about comfort and good decision-making.

That said, the longer the fast (especially 48–72+ hours), the more conservative you should be—particularly if it’s your first time, you’ve had very low intake for multiple days, or you’re not sure you’re starting from a well-nourished baseline.

There’s also a separate category: refeeding syndrome.

What is refeeding syndrome (and who’s at risk)?

Refeeding syndrome is a potentially serious set of electrolyte and fluid shifts that can happen when calories—especially carbohydrates—are reintroduced after severe undernutrition. It’s commonly associated with drops in phosphorus, potassium, and/or magnesium, and it may also involve thiamine deficiency and organ dysfunction (da Silva et al., 2020; Woo Ha & Hong, 2024; Borriello et al., 2025; Cleveland Clinic, 2022).

You should not DIY a refeed if you’re at high risk of malnutrition. Clinical screening criteria commonly include low BMI, large recent weight loss, and little/no intake for multiple days (NICE, 2017; BAPEN, 2024).

If any of these apply, get medical guidance:

• little or no food for 5+ days
• large recent unintentional weight loss
• underweight or suspected malnutrition
• history of eating disorder
• heavy alcohol use disorder
• low potassium/phosphate/magnesium on labs

---

What happens in your body when you refeed (plain-English version)

Here’s the simple mechanism behind “why slow is smart,” especially after longer fasts:

1. Carbs raise insulin.
2. Insulin moves glucose (and electrolytes) into cells. If someone is severely undernourished, that shift can rapidly lower blood levels of phosphate/potassium/magnesium when body stores are already depleted (Borriello et al., 2025).
3. Your gut may need a warm-up. After a longer fast, many people find that huge, greasy, or very high-fiber meals feel rough—so the “start small, go gentle” approach is mainly about comfort and tolerance.

---

A simple refeed rule of thumb (comfort-only)

Some fasting communities use an anecdotal, comfort-focused rule of thumb:

Gentle refeed hours ≈ 0.5 × fast hours

This is not a clinical guideline. It’s just a reminder that the longer the fast, the more you’ll usually do better with a ramp-up.

Safety note: If you have any malnutrition risk (or you’re doing multi-day fasts with very low intake), this article isn’t a substitute for medical guidance.

Examples

If you want an evidence-based parallel (not from the fasting world): in clinical nutrition support, people who have eaten little or nothing for several days are typically restarted below full needs and advanced gradually to reduce complications (NICE, 2017).

---

The 4-phase refeed plan (use this for any fast)

If you’re not sure what to eat, this structure keeps things simple.

Phase 1 — “Wake up” (first 1–2 hours)

Goal: start small, hydrate, and add some sodium.

Good options:

• broth or a light soup
• yogurt or kefir
• a small protein shake

Phase 2 — “Easy solids” (2–6 hours)

Goal: protein + easy carbs + cooked produce.

Good options:

• eggs + cooked zucchini/spinach
• fish or chicken + rice/potato
• oatmeal/cream of rice + Greek yogurt

Phase 3 — “Normal-ish meals” (6–24 hours)

Goal: return to normal portions without going straight to high-fat/high-fiber overload.

Good options:

• a balanced plate (protein + carbs + cooked veggies)
• fruit in small portions

Phase 4 — “Back to baseline” (24–36+ hours)

Goal: resume your usual whole-food pattern.

This is where most people can bring back:

• big salads
• beans/lentils
• nuts/seeds
• spicier foods

If your stomach still isn’t thrilled, just hang out in Phase 2–3 foods a bit longer.

---

Protocols by fast length (16h, 24h, 48h, 72h+)

1) How to refeed after a 16–24 hour fast (16:8, one meal a day)

For a shorter fast, you typically don’t need a complicated protocol. You mainly want to avoid a glucose roller coaster and the “I’m starving so I’ll eat anything” trap.

A simple first meal template:

• Aim for ~20–40 g protein (eggs, Greek yogurt, cottage cheese, tofu, chicken, fish, or a shake)
• add carbs if you want (fruit, oats, rice, potatoes)
• add produce (cooked veggies are often easiest)

That 20–40 g range is a common sports nutrition guideline for “protein per meal” to support muscle protein synthesis, but it’s not a magic number—your needs depend on body size, training, and total daily protein (Jäger et al., 2017).

If you want help choosing a daily protein target, start with BodySpec’s Protein Primer.

Small trick that works: eat your first plate, then wait 20–30 minutes before deciding on seconds.

2) How to refeed after a 36–48 hour fast

This is the sweet spot where a gentle refeed usually pays off immediately.

Hour 0: hydrate first

• water + a salty food, or a low-sugar electrolyte drink
• deeper dive: Electrolytes & Hydration

Hour 0.5–1: small starter

• broth/soup, yogurt/kefir, or a small shake

Hour 1–3: easy solid meal

• eggs or fish + cooked veg
• rice/potato if you want carbs back in gently

Hour 3–24: 1–2 more meals
Keep it “boring but effective”:

• lean protein
• cooked vegetables
• moderate carbs

3) How to refeed after a 72+ hour fast

This is where you should be most conservative, and where medical guidance matters more if your intake has been very low or you’re at malnutrition risk.

A practical 36-hour ramp-up:

• 0–12 hours: mostly liquids + very soft foods (broth/soup, yogurt/kefir, well-cooked vegetables)
• 12–24 hours: small solid meals (eggs/fish/chicken + rice/potato/oats)
• 24–36 hours: normal meals, then slowly reintroduce higher fiber/fat

If you’re running longer fasts regularly, it’s smart to track body composition over time—because a scale can’t tell whether you’re losing fat, water, or lean tissue. (More on that here: Body composition vs. weight and what “lean mass” really means.)

---

Best foods to break a fast (and foods to save for later)

These are “usually gentle” picks—not rules.

Best first foods (many people tolerate well)

• eggs
• yogurt/kefir
• fish or chicken
• rice, oats, potatoes
• cooked zucchini, spinach, carrots
• ripe fruit in small amounts

This general “easy-to-digest and simple” approach is consistent with therapeutic fasting reintroduction protocols (Buchinger Wilhelmi, 2020).

Foods that commonly cause regret on day 1

• very greasy/fried meals
• huge raw salads (especially cruciferous veg)
• very spicy foods
• lots of nuts/seeds (harder to digest)
• alcohol on an empty stomach

What about fermented foods?

Fermented foods (yogurt, kefir, kimchi, sauerkraut) can be a nice add-on if you already tolerate them. In a 10-week randomized trial in healthy adults, a diet high in fermented foods increased microbiome diversity and reduced several inflammatory markers (Stanford Medicine, 2021).

Practical takeaway: start with a small amount, and don’t force it if you’re sensitive.

---

Myth-busting: common refeed mistakes

Myth 1: “Refeeding syndrome happens to everyone after a 24–48 hour fast.”
Reality: refeeding syndrome is primarily linked to severe undernutrition and involves specific electrolyte shifts—not just “my stomach feels weird” (Cleveland Clinic, 2022).

Myth 2: “You should break your fast with pure carbs to ‘turn metabolism back on.’”
Reality: some people feel shaky, sleepy, or “off” after a big refined-carb hit—especially after fasting. Rapid blood sugar swings may contribute to these kinds of symptoms in certain situations, including reactive hypoglycemia after meals (Cleveland Clinic, 2022). A mixed meal (especially with protein) is often smoother.

Myth 3: “Intermittent fasting automatically protects muscle.”
Reality: total protein and training matter most. But meal timing can matter too. A foundational crossover study found 24-hour muscle protein synthesis was higher when protein was spread more evenly across meals (vs. heavily skewed to dinner) (Mamerow et al., 2014).

More recent sports nutrition analysis suggests it’s reasonable to aim for protein spread across meals (especially if your eating window is short), but also notes that total daily protein intake is likely the bigger lever for most people (Trommelen et al., 2024).

The practical takeaway: if your fasting schedule compresses eating into fewer meals, you may need to be more intentional about hitting your protein target.

Myth 4: “Bone broth is mandatory.”
Reality: broth can be convenient. It’s not required. If eggs or yogurt work better for you, that’s fine.

---

Why your DXA scan can look “weird” right after a fast

DXA is the technical term; “DEXA” is a common alternate spelling.

If you get a DXA scan immediately after a fast, don’t be surprised if “lean mass” looks lower than usual.

DXA lean mass includes water. Glycogen (stored carbohydrate) is stored with water, and a sports nutrition review notes that each gram of glycogen is stored with at least ~3 grams of water (Murray & Rosenbloom, 2018).

Also, research in active adults shows dehydration and glycogen changes can significantly shift DXA-based lean tissue measurements—without meaningful changes in fat mass—so consistency matters when you’re tracking trends (Toomey et al., 2017).

Practical tip: If you want clean “before vs. after” comparisons, try to scan under similar conditions each time (similar hydration, similar recent food/exercise). BodySpec’s checklist is here: Prepare for your BodySpec scan.

When you’re ready to track progress, you can book directly here: Book a BodySpec scan. (If you’re comparing options, our guide is here: DEXA scan near me.)

---

Troubleshooting: if your refeed feels awful

If you get loose stools

Common triggers are too much fat too soon or simply eating a very large meal.

Try:

• smaller portions
• simpler carbs (rice/oats/potato)
• leaner protein for 1–2 meals

If you get bloating and gas

Try temporarily going lower on:

• raw vegetables
• beans
• high-fat meals

…and higher on:

• soups
• cooked vegetables
• easier starches

If you feel the “binge urge”

Two strategies that help:

1. Pre-plan your first meal before you start fasting.
2. Break your fast with a structured plate, then wait 20–30 minutes before seconds.

---

Summary: safe refeed checklist

• Start smaller than you think you need.
• Prioritize protein in the first real meal.
• After 36+ hours, go easier on fiber and fat on day 1.
• Hydrate and include sodium.
• If you’re at risk for malnutrition, refeed with medical supervision.

---

FAQ

How do you refeed after a fast without gaining all the weight back?

Break the fast with a smaller, protein-forward meal and ramp portion size back to normal over 12–36 hours (depending on fast length). “Celebration meals” are the most common reason people overshoot.

What’s the best first meal after a 24-hour fast?

Most people do well with a normal balanced meal—just make it protein-forward and avoid starting with a very greasy or very sugary meal.

What’s the best first meal after a 72-hour fast?

Start smaller: broth/soup, yogurt/kefir, eggs, fish, rice/potato/oats, and cooked vegetables. Increase fiber and fat more gradually over the next 24–36 hours.

How long should you refeed after a 48-hour fast?

A practical comfort-focused target is about 24 hours of gentler eating, then return to normal if you feel good.