What is reverse dieting?

Reverse dieting is a structured protocol for gradually increasing calorie intake after a prolonged deficit. Extended cutting suppresses NEAT (non-exercise activity thermogenesis) and down-regulates thyroid hormones and leptin — collectively called metabolic adaptation. A slow calorie ramp gives the metabolism time to readjust without the large surplus that would result from jumping straight to maintenance, which tends to trigger rapid fat re-gain.

How does this calculator work out my calorie target?

It uses the Mifflin-St Jeor equation for BMR: (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5 for males, −161 for females. That is then multiplied by your activity factor (1.2 to 1.9) to get TDEE. The ramp schedule adds your chosen weekly increase each week until daily calories equal TDEE.

How much fat will I gain during a reverse diet?

The calculator estimates fat gain by totalling the cumulative kcal surplus over the ramp period and dividing by 7,700 kcal/kg (the standard energy density of adipose tissue). Because the ramp is gradual, the total surplus is small — a 12-week ramp at +75 kcal/week from a 400 kcal deficit produces a cumulative surplus of roughly 3,150 kcal, or about 0.4 kg of fat. In practice some of that goes to refilling muscle glycogen and water, so real fat gain is often lower.

Should I use 50 kcal or 100 kcal weekly increases?

It depends on how long you dieted, how aggressive the cut was, and how much fat re-gain you can tolerate. A general guideline: if you dieted for more than 12 weeks or dropped below 1,200–1,500 kcal/day, use 50–75 kcal/week for a slower, safer ramp. If the cut was shorter or less severe, 100–150 kcal/week is reasonable. Competitive physique athletes often use 50 kcal/week post-show to protect conditioning.

Can I skip reverse dieting and go straight to maintenance?

You can, but research on post-diet rebound suggests that jumping from a large deficit directly to estimated maintenance still represents a significant surplus relative to the down-regulated metabolic rate — so a faster-than-expected fat regain is common. Reverse dieting is optional but valuable when fat minimisation during the transition is a priority.

Does reverse dieting raise TDEE over time?

Yes, in two ways. First, gradual increases allow NEAT to recover — studies show that NEAT can drop by 300–500 kcal/day during aggressive cuts (Rosenbaum & Leibel, 2010). Second, increased training performance from more fuel leads to greater muscle retention and adaptation. The TDEE figure in this calculator is a static estimate based on your current weight and activity; your real TDEE will likely increase as the reverse diet progresses.

Reverse Diet Calculator

After weeks or months of eating in a calorie deficit, jumping straight back to maintenance can feel like a metabolic landmine — the body’s energy-regulating hormones (leptin, ghrelin, thyroid T3) are suppressed, non-exercise activity thermogenesis (NEAT) has dropped, and the true maintenance intake is temporarily lower than the pre-diet TDEE. Eating at what the calculator predicts as maintenance can therefore produce an unexpected surplus. Reverse dieting solves this by ramping calories back up in small weekly increments, giving the metabolism time to readapt before reaching full maintenance.

This calculator works out your personalised ramp schedule: it computes your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation, then generates a week-by-week table from your current diet calories up to TDEE at whatever weekly increase you choose. Every row shows the daily calorie target, the running kcal surplus, and an estimate of how much fat that surplus could add.

How the formula works

Step 1 — BMR via Mifflin-St Jeor (1990)

BMR = (10 × W) + (6.25 × H) − (5 × A) + S

where W is weight in kg, H is height in cm, A is age in years, and S is +5 for males or −161 for females. Mifflin-St Jeor consistently outperforms the older Harris-Benedict equation in validation studies (Frankenfield et al., 2005) and is the standard choice in clinical dietetics.

Step 2 — TDEE

TDEE = BMR × activity multiplier

The multiplier runs from 1.2 (sedentary) to 1.9 (very active), based on the physical activity levels established by the FAO/WHO/UNU (2004) expert consultation.

Step 3 — Ramp schedule

The week-by-week schedule is straightforward arithmetic:

Cals(n) = start_calories + (n − 1) × weekly_increase
capped at TDEE when the gap is closed.

Step 4 — Fat gain estimate

The cumulative kcal surplus over the ramp equals the sum of each week’s daily surplus × 7 days:

Total surplus = 7 × weekly_increase × W × (W − 1) / 2

where W is the number of weeks. Dividing by 7,700 kcal/kg (the widely-cited energy density of human adipose tissue, derived from biochemical composition data) gives the upper-bound fat gain estimate. In practice, a portion of the surplus refills muscle glycogen and drives increased activity, so actual fat gain is typically lower.

Worked example

A 28-year-old woman, 165 cm, 62 kg, lightly active (×1.375):

BMR: (10 × 62) + (6.25 × 165) − (5 × 28) − 161 = 1,420 kcal/day
TDEE: 1,420 × 1.375 ≈ 1,953 kcal/day

She has been dieting at 1,400 kcal/day — a 553 kcal deficit. Using a 75 kcal/week increase:

Weeks to maintenance: ceil(553 ÷ 75) = 8 weeks
Cumulative surplus: 7 × 75 × 8 × 7 ÷ 2 = 14,700 kcal
Estimated fat gain: 14,700 ÷ 7,700 ≈ 1.91 kg (≈ 4.2 lb)

Compared to jumping straight to 1,953 kcal (a 553 kcal/day surplus for weeks while the metabolism readjusts), the gradual ramp typically results in far less fat re-gain — many practitioners report 0.5–1 kg of real fat gain over an 8-week reverse, with the balance going to glycogen and water.

Starting kcal	TDEE	Weekly increase	Weeks	Est. fat gain
1,400	1,953	50 kcal	12	1.91 kg
1,400	1,953	75 kcal	8	1.27 kg
1,400	1,953	100 kcal	6	0.96 kg
1,200	1,800	50 kcal	12	1.24 kg

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