Who the Fat Loss Sprint Is Best For

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

Note: The profile described here identifies who is likely to benefit most from this protocol based on research and protocol design. Meeting this profile does not guarantee results, nor does not meeting it mean the protocol will not work for you. Individual suitability should be assessed with your health professional.

The Fat Loss Sprint's benefits are greatest, and its risks lowest, when it is used by the right people in the right circumstances. This chapter identifies those populations clearly — so you can make an informed decision about whether it's right for you, and so healthcare professionals can guide their patients accordingly.

Primary Suitability Criteria

Clinical guidelines and research on VLCD and PSMF protocols converge on these primary criteria:

Adults with Obesity (BMI 30 or above)

The Fat Loss Sprint is most strongly supported for individuals with a BMI of 30 or above. At this level of excess body fat, the risk-benefit ratio clearly favours aggressive intervention:

• Sufficient fat stores to fuel rapid fat loss without excessive lean mass compromise
• Obesity-related health risks that benefit from rapid reduction in body mass
• Greater absolute fat loss potential per unit of time
• Lower risk of the adverse effects associated with very low calorie intake that increase at leaner levels

(National Heart, Lung, and Blood Institute, 1998)

Adults with Overweight Plus Comorbidities (BMI 27–29.9)

For individuals with a BMI between 27 and 30 who also have obesity-related health conditions, the sprint may also be appropriate. Qualifying conditions include:

• Type 2 diabetes or prediabetes (HbA1c 5.7% or above)
• Hypertension (blood pressure 130/80 mmHg or above)
• Dyslipidaemia (elevated LDL, triglycerides, or low HDL)
• Obstructive sleep apnoea
• Non-alcoholic fatty liver disease (NAFLD)
• Polycystic ovary syndrome (PCOS)
• Osteoarthritis of weight-bearing joints
• Cardiovascular disease risk factors

In these cases, the medical benefits of rapid weight loss may outweigh the risks of a more conservative approach — particularly where slower methods have already been attempted without success.

Generally Healthy Adults Without Contraindications

The candidate should be in generally good health aside from excess weight. Absolute contraindications (Type 1 diabetes, active eating disorders, pregnancy, severe organ disease) rule out sprint participation regardless of BMI.

Characteristics Associated With Stronger Results

Beyond the basic criteria, these factors are associated with particularly strong outcomes:

Populations That Benefit Most

1. People with Type 2 Diabetes

The sprint offers particularly compelling benefits for people with Type 2 diabetes:

• Rapid glycaemic improvement: PSMF protocols have demonstrated HbA1c reductions of 1–3% and fasting glucose drops of up to 46 mg/dL within weeks
• Medication reduction: Many people can reduce or discontinue diabetes medications during and after the sprint — work with your prescribing doctor to adjust medications as your results develop.
• Visceral fat reduction: The visceral fat stores most closely linked to insulin resistance are preferentially mobilised during severe caloric restriction
• Potential remission: The DiRECT trial demonstrated that intensive caloric restriction produced diabetes remission in 46% of participants at 12 months

(Lean et al., 2018, The Lancet)

People with Type 2 diabetes on insulin or sulfonylureas will typically need their medications adjusted before starting — this requires close coordination with their prescribing physician to prevent hypoglycaemia. The FLS protocol is not appropriate to begin without that medical involvement in place.

2. Pre-Surgical Patients

Surgeons frequently require weight loss before elective procedures:

• Bariatric surgery: Many surgeons require 5–10% weight loss before gastric bypass or sleeve gastrectomy to reduce liver size and surgical risk
• Joint replacement: Orthopaedic surgeons often require BMI reduction before hip or knee arthroplasty
• Hernia repair: Reduced abdominal adiposity improves surgical outcomes
• Cosmetic procedures: Achieving a target weight before body contouring surgery

The sprint provides a time-efficient, medically structured path to meeting pre-surgical requirements.

3. People with Obstructive Sleep Apnoea

Weight loss of 10–15% can significantly reduce or eliminate obstructive sleep apnoea in many people. The sprint achieves this magnitude of loss in 8–16 weeks, providing rapid improvement in a condition with serious cardiovascular and quality-of-life consequences.

4. Women with PCOS

Polycystic ovary syndrome is closely linked to insulin resistance and excess body fat. Weight loss of 5–10% can restore ovulatory cycles, improve insulin sensitivity, reduce androgen levels, and improve fertility outcomes. The sprint's rapid, visible results can be particularly motivating for women planning pregnancy.

5. People Facing Career or Life Milestones

The sprint provides a structured, science-backed alternative to crash diets that people turn to before:

• Military or law enforcement fitness standards
• Athletic competitions with weight classes
• Career opportunities linked to physical fitness standards
• Personal milestones: weddings, reunions, vacations

When the real-world choice is between an unstructured crash diet and a properly designed sprint, the structured protocol is the safer option.

6. People Who Have Failed Conventional Approaches

Repeated failed attempts at moderate caloric restriction create a cycle of frustration and learned helplessness. The sprint offers several specific advantages for this group:

• A fundamentally different approach — the novelty can reignite motivation
• Rapid visible progress combats the discouragement that drives dropout during slow diets
• A defined endpoint. Knowing the sprint has a specific duration, rather than "diet until you reach your goal," reduces psychological burden.
• Higher completion rates. The Purcell RCT (2014) showed 81% of the rapid weight loss group achieved their target vs. only 50% of the gradual group.

Experienced Dieters: A Special Category

Bodybuilders, athletes, and fitness enthusiasts with lower body fat percentages (15–25% for men, 25–35% for women) can use modified sprint protocols — but with important adjustments.

Appropriate modifications:

• Shorter sprint duration: Sprint Level 1 only (14 days) — do not extend to Level 2 or 3 at leaner body fat levels
• Higher protein intake: 2.5–3.0 g/kg LBM (upper end of the FLS range) to protect lean mass at lower body fat levels
• More frequent refeeds: every 3–5 days rather than every 7–14
• More frequent diet breaks: every 3–4 weeks
• Close monitoring of training performance as a proxy for lean mass status

Classic PSMF vs Fat Loss Sprint — duration and protein at lower body fat:

Parameter	Classic PSMF	Fat Loss Sprint
Duration	Open-ended, 2–12+ weeks	Fixed: exactly 14, 21, or 28 days (Sprint Level 1/2/3)
Protein target	1.2–1.5 g/kg ideal body weight	2.2–3.0 g/kg lean body mass (higher absolute intake; LBM-based target is more precise)

For experienced dieters at lower body fat, use Sprint Level 1 (14 days) with protein at the upper end of the FLS range (2.5–3.0 g/kg LBM). The fixed duration gives a defined finish line (adherence) and the higher protein target better protects lean mass under severe restriction (lean mass protection).

When the sprint is appropriate for this group:

• Preparing for a physique competition or photo shoot
• Cutting after a bulking phase
• Achieving a specific body composition goal with a defined timeline

When the sprint is NOT appropriate for this group:

• Already at low body fat (below 12% for men, below 20% for women) — risks increase substantially at these levels
• During a competitive athletic season where performance is the priority
• When disordered eating patterns are present or developing

Medical Screening Before Starting

Recommended Pre-Sprint Evaluation

Required for all participants:

• Complete medical history and physical examination
• Body weight, height, BMI, and waist circumference
• Blood pressure
• Fasting blood glucose and HbA1c
• Complete metabolic panel (electrolytes, kidney function, liver function)
• Complete blood count
• Lipid panel (total cholesterol, LDL, HDL, triglycerides)
• Thyroid function tests (TSH, free T4)

Additional tests for specific populations:

• ECG for individuals over 50 or with cardiac risk factors
• Uric acid levels (risk of gout exacerbation during rapid weight loss)
• Gallbladder ultrasound if history of gallstones
• Pregnancy test for women of childbearing age

Medication review:

All current medications should be reviewed by a prescribing physician, with particular attention to:

• Diabetes medications (insulin, sulfonylureas): dose reduction typically needed as glucose drops
• Antihypertensives: dose reduction may be needed as blood pressure falls
• Anticoagulants: dietary changes may affect vitamin K intake
• Psychiatric medications: some cause weight gain or interact with dietary changes
• Diuretics: electrolyte monitoring becomes more critical

Ongoing Monitoring During the Sprint

Summary

• The sprint is most appropriate for adults with BMI 30 or above, or BMI 27–29.9 with obesity-related comorbidities.
• The best candidates are generally healthy individuals with higher body fat percentages, motivation for structured protocols, and access to resistance training.
• Populations that benefit most: people with Type 2 diabetes, pre-surgical patients, those with obstructive sleep apnoea, women with PCOS, people facing career or life milestones, and those who have failed conventional approaches.
• Experienced dieters with lower body fat can use modified protocols: shorter durations, higher protein targets, and more frequent refeeds and diet breaks.
• Medical screening before starting is recommended and would typically include a full physical exam, comprehensive blood work, and medication review — particularly for anyone with pre-existing conditions.
• For those with relevant health conditions, ongoing monitoring during the sprint may include daily weight checks, blood pressure monitoring, and periodic blood work. The appropriate level of monitoring is a conversation between you and your health professional.
• Sprint Level classification — not "category" — determines your sprint duration and structure. Use your Sprint Level to guide every calculation.