What exactly do you eat on a fasting-mimicking diet?

The ProLon kit provides pre-portioned soups, nut-based bars, kale crackers, olives, herbal tea, and a glycerol-based drink. Day 1 provides roughly 1,100 kcal (10% protein, 56% fat, 34% carbohydrate — a transition day). Days 2 through 5 provide 725–750 kcal per day (9% protein, 44% fat, 47% carbohydrate). Day 6 is a gentle refeed with steamed vegetables, broth, and small portions of complex carbohydrate before returning to normal eating on Day 7. A DIY version using whole foods (kale, chickpeas, olives, nuts, herbal tea) following the same macro targets is possible at roughly a quarter of the kit cost.

Who should not do a fasting-mimicking diet?

The FMD is contraindicated in type 1 diabetes (DKA risk), pregnancy and breastfeeding, active or past eating disorder, BMI under 19 or significant unintentional weight loss, active malignancy outside a supervised trial, recent surgery within 4 weeks, severe liver or kidney impairment, uncontrolled gout, and age under 18. Insulin-treated or sulfonylurea-treated diabetes requires specialist co-management — both medication classes need dose reduction or cessation before and during the cycle. SGLT2 inhibitor users must cease the medication at least 3 days before starting to reduce euglycaemic DKA risk.

How much weight will I lose on a fasting-mimicking diet?

The Wei 2017 randomised trial reported roughly 2.5 kg weight loss per three-cycle course, with partial regain at 3 months after stopping. Much of the initial loss is water associated with glycogen depletion. FMD delivers considerably less sustained weight reduction than a 12-week very-low-calorie diet (such as the DiRECT programme), which produces 10–15 kg loss and meaningful type 2 diabetes remission rates. If weight loss is the primary goal, the evidence supports a structured VLCD programme over FMD.

Is the ProLon kit worth the cost?

The ProLon kit costs roughly AU$350–400 per cycle and is not covered by health funds or PBS. It offers convenience, standardised macros matching the published trial protocol, and a polished user experience. A carefully tracked DIY version using whole foods costs AU$50–80 per cycle and achieves the same macronutrient targets, though no head-to-head trial has compared outcomes. For most patients, the evidence does not support the premium unless adherence depends on convenience and pre-portioning.

Should I adjust my blood pressure or diabetes medications before a fasting-mimicking diet?

Yes — medication adjustment is essential and should be planned with your GP before starting. Sulfonylureas (such as gliclazide) should be withheld at least 24–36 hours before Day 1 and not restarted until normal eating resumes. SGLT2 inhibitors must be ceased at least 3 days before the cycle. Antihypertensives, particularly diuretics and ACE inhibitors, often need dose reduction by 25–50% during the cycle as blood pressure typically falls. Warfarin users need an INR check around Day 5. Lithium users require careful hydration and may need a level check.

Fasting-mimicking diet — cardiometabolic risk reduction

Fasting-Mimicking Diet (FMD / ProLon): evidence and GP guide

By Dr HB Lo, FACRRM Reviewed 28 October 2026 8 min read

The fasting-mimicking diet (FMD) is a 5-day, low-calorie, plant-based eating cycle engineered to replicate fasting physiology while permitting modest food intake.

A 2025 meta-analysis of 11 RCTs shows modest reductions in weight, blood pressure, IGF-1, and HbA1c, largely attributable to caloric restriction. FMD is not TGA-registered, not PBS-subsidised, and does not replace guideline-aligned pharmacotherapy.

Screening for eating disorder history, diabetes medications requiring dose adjustment, and surgical timing is essential before endorsing it.

What the fasting-mimicking diet is

The fasting-mimicking diet (FMD) is a 5-day, low-calorie, low-protein, plant-based eating pattern designed to produce the biochemical state of a multi-day water fast while permitting enough food to make the protocol outpatient-feasible and safer than true prolonged fasting. It was developed by Valter Longo’s group at the USC Longevity Institute and commercialised as the ProLon kit by L-Nutra.

The biological premise: restricting calories, protein, and carbohydrate tight enough to suppress nutrient-sensing pathways — mTOR, IGF-1, PKA, insulin — and shift the body into a ketogenic, autophagic low-IGF state, capturing the metabolic benefits of fasting while retaining outpatient tolerability.

For Australian general practitioners, the key questions are: does the evidence support recommending it, who is safe to do it, what medication adjustments are required, and how does it fit alongside guideline-aligned treatment?

A. Core clinical — the AU general-practice framework

Macronutrient structure

Per the Brandhorst 2015 Cell Metabolism protocol:

Day 1 (~1,100 kcal, 10% protein / 56% fat / 34% carbohydrate): transition day — slightly higher calorie; vegetable soup, nut bar, olives, kale crackers, herbal tea, glycerol-based hydration drink.
Days 2–5 (~725–750 kcal, 9% protein / 44% fat / 47% carbohydrate): soup, olives, crackers, tea, glycerol drink only.
Day 6 refeed: light easily digested foods — steamed vegetables, broth, small complex carbohydrate, small lean protein portion; normal eating resumes Day 7+.

Pre-FMD assessment checklist

RACGP obesity guidelines and eTG endocrinology inform the pre-FMD workup:

Confirm indication and rule out contraindications (see below)
Baseline measurements: weight, BMI, waist circumference, blood pressure
Bloods: FBC, UEC + eGFR, LFTs, HbA1c, fasting glucose, fasting lipids, urate, TSH, vitamin D, B12, ferritin
ECG if cardiometabolic risk or pharmacotherapy (particularly for cardiac rhythm concerns)
Medication review — see medication-adjustment section below
Eating disorder screen using the SCOFF questionnaire: the 2023 clinical advisory (PMC) highlights that caloric restriction protocols can precipitate or worsen disordered eating

Contraindications

Absolute: type 1 diabetes (DKA risk); pregnancy or breastfeeding; active or past eating disorder or disordered eating; BMI under 19 or significant unintentional weight loss; active malignancy outside a supervised oncology trial; recent surgery within 4 weeks or major medical illness; severe hepatic or renal impairment; uncontrolled gout; insulin-treated or sulfonylurea-treated diabetes without specialist co-management; age under 18.

Relative: age over 75; immune compromise; active infection; cardiovascular instability.

Medication-adjustment protocol

Per Grajower & Horne (Cleve Clin J Med 2017) and AMH:

Sulfonylureas (gliclazide, glimepiride): withhold at least 24–36 hours before Day 1; restart only when normal eating resumes Day 7+.
Insulin: mandatory specialist input. Basal insulin typically reduced 30–50%. Most insulin-managed patients should defer FMD or proceed only under endocrinology supervision.
SGLT2 inhibitors: cease at least 3 days before the cycle to reduce euglycaemic DKA risk — a documented safety concern per AMH.
Antihypertensives: reduce diuretic dose and consider 25–50% reduction of ACE inhibitor or ARB if baseline blood pressure is at the lower margin; daily home blood-pressure monitoring during the cycle.
Warfarin: INR check around Day 5 — vitamin K intake falls with plant-only diet.
Lithium: dehydration drives toxicity; ensure adequate hydration (~2 L/day) and check lithium level if undertaking repeat cycles.

Cycle scheduling

The Wei 2017 RCT protocol used 3 monthly back-to-back cycles for the initial response; the largest cardiometabolic changes occurred within this initial phase. Maintenance is typically quarterly or twice-yearly after the initial 3 cycles. A Mediterranean-pattern diet between cycles preserves benefit; an unrestricted Western diet between cycles largely negates it.

B. Evidence appraisal — what the trials actually show

What benefits have been demonstrated

The Wei 2017 randomised trial (n=71, 3 FMD cycles) — the foundational human RCT — showed reductions in weight (~2.5 kg), systolic blood pressure, IGF-1, fasting glucose, and C-reactive protein versus controls. A 2025 meta-analysis of 11 RCTs confirmed consistent HbA1c, IGF-1, and blood pressure reductions across trials. A 2024 Nature Communications study (n>200 across 2 RCTs) reported an estimated biological-age reduction of ~2.5 years on epigenetic clocks — though clock validity as a clinical endpoint is actively debated.

Bottom line on cardiometabolic markers: real, but modest. Effect sizes are within the range achievable by any caloric restriction of similar magnitude.

What has not been demonstrated

No head-to-head RCT versus isocaloric restriction matched at 750 kcal/day with the same macronutrient ratio. The specific macronutrient pattern may add to, or may not add to, simple caloric deficit.
No hard outcome data (cardiovascular events, stroke, cancer incidence, or mortality reduction).
No durable type 2 diabetes remission from FMD alone. The DiRECT trial (Lancet 2018) demonstrated meaningful T2DM remission, but via 12 weeks of VLCD producing 10–15 kg sustained weight loss — a far higher bar than FMD delivers.
No benefit as cancer adjuvant outside a supervised trial. The Caffa 2020 Nature paper showed a preclinical and early human signal for FMD combined with endocrine therapy in hormone-receptor-positive breast cancer. This is investigational only — patients must not self-administer FMD during cancer treatment.

Commercial conflict of interest

The majority of positive FMD trials have been conducted by or in collaboration with Longo’s group at USC, where the L-Nutra/ProLon commercial entity has institutional ties. As STAT News documented in 2017, this creates a significant unresolved conflict of interest. Independent replication by groups without L-Nutra ties remains limited. Clinicians should counsel patients on this context when discussing the evidence base.

C. ProLon kit versus DIY — practical guidance

The ProLon Australia kit costs roughly AU$350–400 per cycle via LifeX Australia. It offers convenience, standardised macros, and fidelity to the published trial protocol. However, it is a commercial food product, not a TGA-registered medicine or therapeutic good — claims must comply with Food Standards Australia New Zealand (FSANZ) requirements.

A DIY FMD following Longo’s published macronutrient targets — kale, chickpeas, carrot, olive, nuts, olive oil, herbal tea, under 5 g salt — achieves the same calorie and macro profile at AU$50–80 per cycle. The main risks are protein creep (especially from nuts, which blunts mTOR/IGF-1 suppression) and difficulty tracking macros precisely without kitchen scales and a food-logging app.

Practical approach: patients with good food literacy and access to kitchen scales may DIY from cycle 2 onward after calibrating the experience on one ProLon kit. Patients using the kit for the first time benefit from the pre-portioning.

For patients with type 2 diabetes, obesity, or MASLD as the primary indication, a Diabetes Australia-credentialled dietitian or accredited practising dietitian under a GPCCMP is strongly preferred over self-guided DIY, given the medication adjustment complexity.

D. Australian operations

MBS billing context

MBS Online items applicable:

Standard consults 23 / 36 / 44: pre-FMD assessment, medication review, mid-cycle check.
GPCCMP 965 / 967: appropriate where FMD is part of a chronic-disease management plan for type 2 diabetes, obesity, hypertension, or MASLD — enables direct referral to an accredited dietitian under the allied-health items.
Heart Health Check 699 / 177: if cardiometabolic risk reduction is the primary indication and the patient qualifies by age.
Pathology: HbA1c, UEC, LFTs, fasting lipids, TSH, vitamin D, B12, ferritin, and FBC under standard MBS pathology items.

ProLon is not PBS-subsidised and not health-fund-rebated as a medicine — some extras policies cover the dietitian consultation but not the food kit. Advise patients accordingly.

Safety netting

Stop the cycle and seek urgent review if: persistent vomiting, confusion, syncope, severe headache, ketone-positive abdominal pain (suspect euglycaemic DKA in SGLT2 inhibitor users — cease the agent at least 3 days before), chest pain, or blood pressure under 90/60 mmHg with symptoms. Document the medication-adjustment plan and contingency advice in the clinical record.

The Heart Foundation 2023 CVD risk guideline remains the primary reference for cardiometabolic targets and pharmacotherapy thresholds — FMD does not displace pharmacotherapy where the risk threshold is met.

E. Special populations

Older adults (>65 years). Greater risk of dehydration, orthostatic hypotension, and muscle catabolism. Pre-cycle protein intake of 1.2 g/kg/day in the preceding week may limit lean-mass loss, though this is extrapolated from prolonged-fasting literature. Light walking and gentle yoga only during the cycle; avoid intense activity.

Patients with type 2 diabetes. Medication adjustment is mandatory. Co-management with an endocrinologist or credentialled diabetes educator is the preferred model per Diabetes Australia’s 2024 handbook. NDSS-funded continuous glucose monitoring (for eligible patients) provides helpful real-time safety monitoring during the cycle.

Patients with MASLD/NAFLD. FMD as a short-course caloric-restriction adjunct is consistent with the ≥10% weight-loss target for fibrosis regression described in Frontiers in Nutrition 2024. A full VLCD or structured low-calorie programme has stronger evidence for sustained fibrosis regression.

Active cancer patients. Do not recommend FMD outside a supervised oncology trial. The evidence base (Caffa 2020) is preclinical and early-phase; risks of sarcopenia and treatment-tolerability compromise are real.

Eating disorder history. Even a past history is an absolute contraindication. The 2023 PMC clinical advisory explicitly identifies caloric-restriction protocols as capable of triggering relapse.

When to escalate

Refer to or involve a specialist when:

Insulin-treated or sulfonylurea-treated type 2 diabetes — endocrinologist or credentialled diabetes educator input required before proceeding
Active MASLD with significant fibrosis — hepatologist input on weight-loss strategy
Suspected eating disorder or borderline SCOFF screen — refer to a Butterfly Foundation-affiliated eating disorder service or specialist eating disorder psychiatrist
SGLT2 inhibitor or other complex medication requiring specialist co-adjustment
Oncology patient requesting FMD — redirect to the treating oncologist; do not endorse outside a trial

What this article is and is not

This is general health information based on current clinical literature — the Wei 2017 trial, meta-analyses, RACGP, eTG, Diabetes Australia, and Heart Foundation guidelines — and is not personal medical advice. Endorsing or supervising FMD for individual patients requires a full clinical assessment by the treating GP or specialist, including medication review and contraindication screening.

For Australian consumer-friendly sources: HealthDirect — Fasting and weight loss, Better Health Channel — Fasting.

For urgent support with eating or food concerns: Butterfly Foundation 1800 33 4673, HealthDirect 1800 022 222.

Sources cited

Frequently asked questions

What exactly do you eat on a fasting-mimicking diet?

The ProLon kit provides pre-portioned soups, nut-based bars, kale crackers, olives, herbal tea, and a glycerol-based drink. Day 1 provides roughly 1,100 kcal (10% protein, 56% fat, 34% carbohydrate — a transition day). Days 2 through 5 provide 725–750 kcal per day (9% protein, 44% fat, 47% carbohydrate). Day 6 is a gentle refeed with steamed vegetables, broth, and small portions of complex carbohydrate before returning to normal eating on Day 7. A DIY version using whole foods (kale, chickpeas, olives, nuts, herbal tea) following the same macro targets is possible at roughly a quarter of the kit cost.
Who should not do a fasting-mimicking diet?

The FMD is contraindicated in type 1 diabetes (DKA risk), pregnancy and breastfeeding, active or past eating disorder, BMI under 19 or significant unintentional weight loss, active malignancy outside a supervised trial, recent surgery within 4 weeks, severe liver or kidney impairment, uncontrolled gout, and age under 18. Insulin-treated or sulfonylurea-treated diabetes requires specialist co-management — both medication classes need dose reduction or cessation before and during the cycle. SGLT2 inhibitor users must cease the medication at least 3 days before starting to reduce euglycaemic DKA risk.
How much weight will I lose on a fasting-mimicking diet?

The Wei 2017 randomised trial reported roughly 2.5 kg weight loss per three-cycle course, with partial regain at 3 months after stopping. Much of the initial loss is water associated with glycogen depletion. FMD delivers considerably less sustained weight reduction than a 12-week very-low-calorie diet (such as the DiRECT programme), which produces 10–15 kg loss and meaningful type 2 diabetes remission rates. If weight loss is the primary goal, the evidence supports a structured VLCD programme over FMD.
Is the ProLon kit worth the cost?

The ProLon kit costs roughly AU$350–400 per cycle and is not covered by health funds or PBS. It offers convenience, standardised macros matching the published trial protocol, and a polished user experience. A carefully tracked DIY version using whole foods costs AU$50–80 per cycle and achieves the same macronutrient targets, though no head-to-head trial has compared outcomes. For most patients, the evidence does not support the premium unless adherence depends on convenience and pre-portioning.
Should I adjust my blood pressure or diabetes medications before a fasting-mimicking diet?

Yes — medication adjustment is essential and should be planned with your GP before starting. Sulfonylureas (such as gliclazide) should be withheld at least 24–36 hours before Day 1 and not restarted until normal eating resumes. SGLT2 inhibitors must be ceased at least 3 days before the cycle. Antihypertensives, particularly diuretics and ACE inhibitors, often need dose reduction by 25–50% during the cycle as blood pressure typically falls. Warfarin users need an INR check around Day 5. Lithium users require careful hydration and may need a level check.

Source quality

Sources grouped by evidence tier. AU primary tier first; international where AU is silent or lagging; named-author reconstruction where guidelines have not yet caught up. How tiers work.