Review · Weight health

Fast Lean Pro review: a fasting idea in a 1.7-gram scoop

Fast Lean Pro is a powder you stir into your morning coffee, sold with the promise that it lets your body "fast" without skipping meals. We transcribed its label and looked up every ingredient on PubMed. The ingredients are reasonable. The amounts are the problem.

By Grant Whitaker, Editor · Updated October 23, 2026 · 16 studies checked on PubMed

This is an independent review page. Stark Verve is not the maker or seller of Fast Lean Pro, and we are compensated with a commission if you buy through our links.

What Fast Lean Pro is

Fast Lean Pro is a tasteless powder in a jar of 30 scoops. The label says to add one scoop (1.7 grams) once or twice a day to 6 to 8 ounces of coffee, tea or another drink. It is distributed by a company named Fast Lean Pro in Aurora, Colorado, and sold through Digistore24 on the seller's own website. The same product, at the same prices, also has a storefront that sells through ClickBank.

The sales page frames it around intermittent fasting. Its story: going without food flips a "fasting switch" that burns fat and clears out old cells, and Fast Lean Pro's six ingredients "trick your brain" into that state whatever and whenever you eat. It mentions Japanese scientists, which appears to point at the autophagy research that won the 2016 Nobel Prize. We look at that claim in its own section below.

What is on the label

The Supplement Facts panel is published on the seller's references page. We read it directly. Per 1.7-gram scoop:

• Niacin: 20 mg (124% of the Daily Value)
• Vitamin B12: 5 mcg (208% DV)
• Chromium: 123 mcg (350% DV); the chemical form is not stated
• Proprietary blend, 1.7 g: Fibersol 2, purified acacia hydrolysate (as Sukre), biogenic polyamine complex. Individual amounts are not disclosed.

The label also notes that the product contains sesame. The seller's terms do not give affiliates permission to reproduce images, so we describe the label here instead of showing it.

Two details matter. First, the blend weighs 1.7 grams and the whole scoop weighs 1.7 grams, so the three blend ingredients together make up essentially the entire serving. Second, the sales page and the label agree on six ingredients, but the FAQ on the same page says the formula has "eleven." We found no sign of the other five, and we treat the label as the authority.

The formula next to the research

For each ingredient we looked for human trials on appetite, fullness or body weight and compared the amounts studied with what one scoop provides. Because the blend amounts are hidden, we use the most generous assumption: that a single fiber filled the entire 1.7 grams.

Fibersol 2: a real satiety signal, at ten grams

Fibersol 2 is a branded digestion-resistant maltodextrin, a soluble fiber. In a randomized, double-blind crossover study, 19 healthy adults (9 men, 10 women) ate a standard meal with tea containing 0, 5 or 10 grams of it. With 10 grams, hunger was delayed and fullness lasted longer for about 90 minutes to two hours, and two gut hormones linked to fullness rose. With 5 grams there was no difference from plain tea ^[1].

That 5-gram result is the key fact for this review. Five grams did nothing measurable, and a scoop of Fast Lean Pro contains less than 1.7 grams of Fibersol 2, shared with two other ingredients. Two scoops a day still land below the amount that failed. A related resistant dextrin taken at 14 grams a day for four weeks raised fasting fullness scores in 36 adults, but energy intake and body measurements did not change ^[2].

Acacia fiber: well tolerated, but studied by the tablespoon

"Sukre" is a trade name for a purified acacia fiber. In 48 healthy adults, 40 grams of acacia gum in orange juice with breakfast increased fullness and reduced hunger at some time points, while 20 grams did less ^[3]. A six-week trial in 120 healthy women in Sudan gave 30 grams of gum arabic a day and reported a small drop in body mass index (0.32 points) and body fat percentage compared with the start; side effects in the first week included bloating, mild diarrhea and nausea ^[4]. That trial enrolled only women, used a pectin placebo at a much smaller dose, and reported within-group changes. It tells us little about men over 50 taking well under 2 grams.

Chromium: the most studied ingredient, with a small effect

Chromium has the most weight research behind it, and the results are modest. A Cochrane review of nine randomized trials (622 overweight adults) found about 1.1 kg more weight loss than placebo after 12 to 16 weeks, an effect the authors called of debatable clinical relevance and rated as low-quality evidence; they found no reliable basis for firm decisions ^[5]. A later meta-analysis of 21 trial arms (1,316 participants) found an average difference of 0.75 kg ^[6]. In an 80-person Yale trial, 1,000 mcg a day for 24 weeks did not change body mass index compared with placebo ^[7]. Fast Lean Pro's 123 mcg sits below every dose in that research.

Polyamines, niacin and B12: no weight evidence we could find

"Biogenic polyamine complex" most likely refers to spermidine-type compounds, which have drawn interest in aging research. The human trials we found did not look at weight. In a 12-month trial of 100 adults aged 60 to 90, 0.9 mg of spermidine a day from a wheat germ extract did not change memory or biomarkers compared with placebo ^[10]. In 37 healthy men aged 50 to 70, 40 mg a day for 28 days was well tolerated and barely changed blood polyamine levels ^[11]. The label gives no amount for this complex.

For niacin, a pooled analysis of 22 trial arms found a small drop in body mass index (about 0.19 points) with no significant change in body weight, and the effect grew with dose ^[9]. Fast Lean Pro provides a standard nutritional amount. We found no trial showing that vitamin B12 supplements help with weight in people who are not deficient.

What the marketing claims and what we could verify

The "fasting switch." Autophagy, the process by which cells break down and recycle their own parts, is real, and its genetic machinery was mapped in baker's yeast by Yoshinori Ohsumi, who received the 2016 Nobel Prize for it ^[13]. That work did not test this formula or any of its ingredients for weight. We found no human study showing that these six ingredients, at these doses, switch on fasting-like fat burning or autophagy.

The seller's own references. The sales page lists about fifty references. Many are news stories about fasting monks. Several of the scientific ones are cell or animal studies. For example, the paper cited for chromium and autophagy was done in kidney cells in a dish ^[12]. The human fiber studies on the list are real, and we cite two of them above, but they used ten grams and more.

Intermittent fasting itself. Even the habit the product imitates has a modest record. A 2026 Cochrane review of 22 randomized trials in adults with overweight found that intermittent fasting may make little to no difference in weight loss compared with regular dietary advice ^[16]. A powder that copies fasting would have to beat a strategy that itself performs about the same as standard advice.

Rejuvenation and appearance. The sales page talks about renewing "every single cell" and looking years younger. We found nothing in the research on these ingredients that supports those statements, so we give them no weight in our score.

Price, packages and refund policy

The seller calls each jar a 30-day supply. At the label's upper use of two scoops a day, a jar lasts about 15 days. Prices on the seller's site when we checked:

• 6 jars: $49 each ($294 total), free US shipping, three digital e-books included.
• 3 jars: $69 each ($207 total), free US shipping.
• 2 jars: $79 each ($158 total), plus $9.99 shipping. There is no single-jar option.

All packages are one-time payments. The refund window is 180 days from delivery, which is generous. The fine print is stricter than the sales page FAQ suggests: the refund policy asks you to send back all the jars with the packing slip, and return shipping is at your expense. Keep your jars and packaging if you want to use the guarantee.

For comparison, the fiber amounts used in the studies above (10 grams or more a day) are easy to reach with a generic soluble fiber powder that costs a fraction of $49 a month.

Safety

At these amounts, the ingredients are unlikely to cause trouble for most healthy adults, and the trials above reported side effects similar to placebo for chromium ^[8] and good tolerance for spermidine ^[11]. Fiber can cause gas and bloating, mostly at much larger doses ^{[3] [4]}. Points to raise with your doctor:

• Blood sugar medication. A meta-analysis of 25 trials in people with diabetes found that chromium lowered HbA1c and fasting glucose ^[8]. If you take insulin or other glucose-lowering drugs, ask your doctor before adding chromium, even at this dose.
• Sesame allergy. The label states that the product contains sesame.
• Niacin. 20 mg per scoop, or 40 mg at two scoops, is above what most multivitamins provide. Niacin can cause skin flushing, a warm, red feeling in the face, a well-documented effect at the larger doses used for cholesterol ^[14]. Count any other niacin you take.
• Thyroid medication. A systematic review of 63 studies found that coffee, fiber and chromium supplements were each linked to lower absorption of levothyroxine ^[15]. This product combines all three in one cup, so if you take thyroid hormone, ask your doctor or pharmacist how far apart to keep them.
• Other medications. Fiber and minerals can change how some pills are absorbed. Your pharmacist can tell you whether to space them out.

The label itself advises consulting a physician if you take medication or have a medical condition. We agree. Results vary from person to person, and any new or worsening symptom deserves medical care, not a supplement.

What we liked and what gave us pause

Frequently asked questions

Where can I buy Fast Lean Pro?

On the seller's website, which processes orders through Digistore24. The seller's affiliate terms forbid listings on Amazon, eBay and similar sites, so listings there may not be genuine or covered by the refund policy.

Does Fast Lean Pro replace intermittent fasting or a diet?

We found no evidence that it does. The best-supported steps for weight management remain eating patterns you can sustain and regular activity, worked out with your doctor if you have health conditions.

How long before I notice anything?

Results vary. The fiber studies measured fullness over a few hours after a single large dose, and the chromium trials ran 12 to 24 weeks with small average effects. We cannot predict what one or two scoops a day will do.

Is it a subscription?

No. Each package is a one-time payment, according to the seller.

How we reviewed Fast Lean Pro

We read the seller's sales page, FAQ, refund policy, affiliate terms and the Supplement Facts label published on its references page. We searched PubMed for human trials of each labeled ingredient on appetite, fullness and body weight, opened every study we cite, and compared the amounts studied with what a scoop provides. We also looked up the scientific references the seller lists. We did not test the product on people, and nobody at Stark Verve is a medical professional. Read our editorial policy to learn how we choose and update reviews. Stark Verve earns a commission if you buy through our links; that never changes what we write about the evidence.