Setting Up Your Fat Loss Sprint

This content is for informational purposes only and does not constitute medical or nutritional advice. Speak with your health professional before starting this protocol.

Setup disclaimer: These calculations set the parameters for your sprint. Errors in your body fat measurement or body weight will flow through every calculation that follows. Double-check your inputs. If your calculated calorie total falls below 800 kcal, increase protein — do not reduce further. If you are unsure about any calculation, consult a registered dietitian.

This is where all the science becomes your specific numbers. Work through each step in order. By the end, you will have everything you need to start your sprint.

Step 0: Determine Your FLS Sprint Level

Your FLS Sprint Level drives every parameter that follows. Get this right first.

Measure Your Body Fat Percentage

If you are an athlete, bodybuilder, or carry above-average muscle mass:

For most people, use the US Navy Circumference Method (tape measure only, ±3–5%):

Measure: waist at the navel, neck below the larynx, hips at the widest point (women only). All measurements in cm.

Step 1 — Calculate body density:

Men:

Density = 1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)

Women:

Density = 1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)

Step 2 — Convert to body fat %:

BF% = (495 ÷ Density) − 450

Assign Your FLS Sprint Level

What Your Sprint Level Controls

Protein is set separately on a sliding scale based on your exact body fat percentage — see Step 4.

Step 1: Calculate Your Lean Body Mass (LBM)

LBM = Total Body Weight × (1 − BF% ÷ 100)

Example: 95 kg at 30% body fat → LBM = 95 × 0.70 = 66.5 kg

Step 2: Calculate Your Fat Mass

Fat Mass = Total Body Weight − LBM

Example: 95 − 66.5 = 28.5 kg fat mass

Step 3: Activity Level (Already Set for You)

All FLS users follow the same prescribed activity level: 2 full-body strength training sessions per week, plus 7,000–10,000 steps per day on non-strength days. This corresponds to a Moderately Active classification.

Your TDEE multiplier is fixed at 1.55 for everyone on the protocol. You do not need to estimate or adjust this.

Step 4: Set Your Protein Target

Protein is set from a continuous sliding scale based on your exact body fat percentage. The leaner you are, the more protein you need to protect lean mass during the deficit. There are no fixed values per sprint level. Your precise BF% determines where you land on the scale.

Sliding scale thresholds:

Protein by BF% position:

Interpolation formula (when your BF% falls within a range):

Protein (g/kg) = Upper endpoint − [(BF% − Range start) ÷ (Range end − Range start)] × (Upper endpoint − Lower endpoint)

Example — Male at 22% body fat (Sprint Level 2 range: 16–25%):

Protein = 2.7 − [(22 − 16) ÷ (25 − 16)] × (2.7 − 2.2) = 2.7 − [6 ÷ 9] × 0.5 = 2.7 − 0.33 = 2.37 g/kg LBM

Then:

Protein (g/day) = g/kg LBM × your LBM (kg) Protein kcal = Protein (g) × 4

Step 5: Set Your Dietary Fat

Fat intake is fixed by your sprint level. It covers essential fatty acid requirements and fat-soluble vitamin absorption.

Most of this fat comes from two sources: fat naturally present in lean protein foods (even lean chicken breast carries approximately 3–4 g fat per 100 g), and your fish oil supplement.

Fat kcal = Fat (g) × 9

Step 6: Carbohydrates from Vegetables

Carbohydrates on sprint days come entirely from non-starchy vegetables, eaten freely. You count net carbs only — total carbs minus fibre. The target is 50 g net per day, and the app allows up to ~70 g before flagging over so a veg-heavy day stays in range. Cruciferous and leafy vegetables are mostly fibre, so eating a generous volume of broccoli, spinach, kale, cucumber, courgette, rocket, and similar vegetables will land comfortably inside that window.

Use 40–60 g net carbs / ~200 kcal as your working estimate for total calculations.

Step 7: Calculate Total Daily Calories and Check the Floor

Total kcal/day = Protein kcal + Fat kcal + Trace Carb kcal

Your calorie total is an output of the macro calculation, not an input. Protein is set first based on your LBM and body fat percentage. Fat is set by sprint level. Carbs follow from your vegetable intake. Calories follow automatically.

800 kcal floor: If your total falls below 800 kcal, increase protein until the 800 kcal minimum is met. Fat and carbs stay fixed.

Floor adjustment formula (if needed):

Extra protein needed (g) = (800 − total kcal) ÷ 4

Step 8: Calculate Your TDEE and Caloric Deficit

Mifflin-St Jeor BMR:

Men:

BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5

Women:

BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161

TDEE = BMR × 1.55 (fixed FLS multiplier) Daily deficit = TDEE − Total daily calories

Step 9: Estimate Your Rate of Fat Loss

Weekly fat loss (kg) = (Daily deficit × 7) ÷ 7,700

7,700 kcal is the approximate energy content of 1 kg of body fat. This is an estimate. Actual results vary with individual metabolic variation and NEAT changes.

Step 10: Confirm Sprint Duration and Refeed Days

These are fixed by your sprint level. They do not change based on how you feel or how the sprint is progressing.

Worked Examples

Example 1: Male, 100 kg, 35% Body Fat

BF% 35% (male) → Sprint Level 3

Example 2: Female, 75 kg, 32% Body Fat

BF% 32% (female) falls in 25–35% range → Sprint Level 2

Example 3: Male, 85 kg, 22% Body Fat

BF% 22% (male) falls in 16–25% range → Sprint Level 2

What to Track During Your Sprint

Track these:

• Protein (grams): your most important daily metric. Hit your target every day.
• Body weight: daily, first thing in the morning, after using the bathroom, before eating. Calculate weekly averages to cut through day-to-day fluctuation.
• Waist circumference: weekly, same time and conditions.
• Step count: daily.

Do not obsess over: Every micronutrient, every calorie, every gram. The protocol is structured so that if you are eating the right foods, your macros land in the correct ranges naturally.

The FLS protocol recommends lean protein at every meal, with the rest of the plate filled with non-starchy vegetables. All listed supplements are taken daily. The training recommendation is 2–3 resistance sessions per week with daily walking.

Food Guidelines

Vegetables: Eat Unlimited

Cruciferous and leafy vegetables are the only category on the Fat Loss Sprint with no portion restriction. Eat as much as you want, every meal, every day.

These vegetables run approximately 15–35 kcal per 100 g. No realistic volume of broccoli, kale, or spinach will meaningfully disrupt your caloric deficit.

Why it matters beyond calories:

• Fibre triggers stretch receptors in the stomach, sending fullness signals before calories even register
• Soluble fibre stimulates GLP-1 and PYY release — satiety hormones that reduce appetite and slow gastric emptying
• High vegetable intake is the most effective dietary solution to the constipation that is otherwise common during a VLCD

Target 300–600 g of vegetables per day.

Recommended: broccoli, cauliflower, cabbage, Brussels sprouts, kale, spinach, rocket, lettuce, courgette, cucumber, celery, asparagus, green beans, mushrooms, bell peppers.

Cook with water, not oil. Steam, boil, roast on a lined tray, eat raw, or stir-fry with water or stock. Do not sauté in butter or oil.

Season freely: salt, pepper, garlic powder, chilli flakes, herbs, spices, lemon juice, vinegar, hot sauce, mustard, soy sauce. All unrestricted.

Build every meal around vegetables first. Add protein on top. A meal built on 300 g of broccoli with 180 g of chicken breast is significantly more filling than the same chicken with a side salad.

Protein Sources: Whole Food First

Whole food protein outperforms powder on every metric that matters during your sprint:

• Greater satiety per gram. Chewing, gastric distension, and slower transit generate stronger fullness signals than a liquid shake providing identical protein.
• Slower digestion. A chicken breast takes 3–5 hours. Whey is largely absorbed within 90 minutes. Whole food provides more sustained amino acid availability.
• Higher micronutrient density. Lean meat and fish provide zinc, iron, B12, selenium, and (for oily fish) omega-3s.
• Slightly higher thermic effect. Processing intact food costs your body more energy than absorbing isolated protein.
• Psychological satisfaction. Eating a real meal takes time, involves chewing and texture, and creates a meaningful psychological experience during an already demanding protocol.

When protein powder is appropriate: post-training (whey protein isolate for fast delivery), when whole food is impractical, or as an end-of-day top-up.

Best powder choice: Whey protein isolate (WPI). Highest protein content per serving (~90%+ by weight), minimal fat and carbohydrates, highest leucine content, fast absorption.

Casein protein is useful as a late-evening dose. It digests over 5–7 hours, providing sustained amino acids overnight during the extended fast.

Protein bars: Most contain 8–15 g fat and 20–40 g carbohydrates per bar. With a total fat allocation of 25–30 g/day, most bars are incompatible with sprint days. Evaluate every bar on its complete macro profile, not just the protein content.

Aim for at least 2 of your 3–4 daily meals to be whole food. One shake per day is fine. If you are relying on more than two shakes per day, restructure toward whole food.

Setup Checklist

Before you start your sprint, confirm you have:

• Measured body fat percentage and assigned your FLS Sprint Level
• Calculated your LBM
• Calculated your protein target (g/day) from the sliding scale
• Confirmed your dietary fat allocation (25/27/30 g/day by sprint level)
• Checked your total calories are above the 800 kcal floor
• Calculated your TDEE and estimated daily deficit
• Confirmed your sprint duration and both refeed days
• Sourced your required supplements (see "Supplementation")

Key Takeaways

• Your FLS Sprint Level (1, 2, or 3) sets every parameter of your protocol.
• Protein is a sliding scale from 2.2 to 3.0 g/kg LBM, interpolated from your exact body fat percentage.
• Fat is fixed by sprint level: 30 g (Level 1), 27 g (Level 2), 25 g (Level 3).
• Your sprint carbs come from non-starchy vegetables, eaten freely — that's the only intentional source. Net carb target is 50 g per day (total carbs minus fibre); the app allows up to ~70 g before flagging over so veg-heavy days stay in range. Off-limits starchy items (potato, corn, peas, etc.) push net carbs out of the sprint range fast.
• If calculated calories fall below 800 kcal, increase protein by the shortfall divided by 4. Fat and carbs stay fixed.
• Activity multiplier is fixed at 1.55 for all FLS users.
• Sprint durations and refeed days are fixed by sprint level and do not change.

References

Bistrian, B. R. (1978). JAMA, 240(21), 2299–2302. https://doi.org/10.1001/jama.1978.03290210069032

Helms, E. R., Aragon, A. A., & Fitschen, P. J. (2014). Journal of the International Society of Sports Nutrition, 11(1), 20. https://doi.org/10.1186/1550-2783-11-20

Mifflin, M. D., et al. (1990). The American Journal of Clinical Nutrition, 51(2), 241–247. https://doi.org/10.1093/ajcn/51.2.241