Customers describe noticeable benefits during multi-day fasts, including mental clarity and fewer cravings by day four or five. Many praise the taste and the convenience of bars, shakes, and multi-day kits. Several reviews mention recurring billing, unwanted shipments, and late deliveries. Shipping fees and a clunky checkout often make ordering harder.
Examples from available reviews (May 2022 – Mar 2026).
Reviewer experienced mental clarity by days four or five and endorses science.
“Day 4 or 5 the mental clarity is the best part.”
Repeated purchases with easy ordering and perceived metabolic health improvements.
“This is my 12th Fasting Mimicking Diet purchase in 13 months.”
Customer was charged for three kits and cannot get resolution.
“Prolon charged me for 3 kits instead of just the 1 kit I wanted.”
Confusing cart process and discounts; forced into subscription without choice.
“It was unclear how to add the original FMD box to the cart.”
Billing and autoship issues drive most negative feedback. Multiple reviewers report surprise charges, shipments continuing after cancellation, and trouble getting refunds. Other reviews share better experiences, including reps replacing missing items or fixing problems quickly.
Value opinions depend on shipping costs and clear pricing. Some reviewers say shipping fees or unannounced price changes wipe out promo savings. Others say clear discounts and free-shipping deals make the program affordable.
Most usability complaints center on checkout and account steps. Reviewers mention confusing cart behavior, a slow site, and problems using FSA/HSA payments or dealing with split charges. In contrast, several customers describe smooth ordering and an easy-to-use site.
Product quality stands out as a consistent positive theme. Users say the bars, shakes, and kit foods taste good and help them stick with short-term fasts. Repeat buyers also mention steady quality across recurring orders.
Communication trends positive, with specific examples of helpful, informative support. Some reviewers point to an active community and responsive staff. A small number mention promised messages that never came or replies that did not help.
Reviews split between strong product results and weak operations. Many customers highlight physical results and good taste, while others focus on serious billing and shipping problems. That contrast shapes the overall view of the buying experience.
For each review, the core experience based on original source reviews.
Sources: Trustpilot (40) · Collected.reviews (1) · Quotes shortened · As of: March 2026
Reviewer experienced mental clarity by days four or five and endorses science.
“Day 4 or 5 the mental clarity is the best part.”
Reviewer reports many benefits and finds claims accurate.
“GREAT!! Lots of great benefits, nothing that I have seen written about positive experiences seems off.”
Shipping costs negate promotional coupons unless buying large quantity.
“Coupons & Costs: You offer promotional deals but then the shipping kills it”
Paid for expedited shipping but delivery was delayed five days.
“I paid extra for expedited shipping thinking I was going to get my package delivered in 2-3 days.”
Received unwanted additional orders and requests refund, calls it a scam.
“Please stop sending your product to me. And please refund my money.”
On day three, reviewer finds products tasty and customer service prompt.
“The kale crackers and various soups are very good”
Finds fast manageable, small meals help; feels good overall.
“I am on Day 4 and am so happy with this fast.”
Appreciated group support via Zoom experts and Facebook community.
“I loved the group support- both Zoom calls with experts and the FB community- through the experience.”
FSA payment was confusing; costs split unexpectedly between cards.
“Excited for your products but was nervous in using my FSA account because it originally was declined”
Reviewer found subscriptions difficult to cancel.
“Challenging to cancel subscriptions.”
Was charged for a kit despite not on autoship and no delivery.
“I was charged to a kit- I was absolutely not on auto shop!!!”
Repeated purchases with easy ordering and perceived metabolic health improvements.
“This is my 12th Fasting Mimicking Diet purchase in 13 months.”
Confusing cart process and discounts; forced into subscription without choice.
“It was unclear how to add the original FMD box to the cart.”
On day four, reviewer and husband feel great nearing completion.
“we are on day 4 today! me and my husband feel great!”
Website was very slow and frustrating to use.
“Website is really, really hard to use.”
Cancelled subscription but deliveries continued; cannot stop autoship.
“I cancelled my subscription they keep sending it!!!!”
Customer service failed to provide the requested day-one email.
“Customer service is not good.”
Customer service provided a helpful workaround for a missing item.
“Excellent service, customer service rep gave me a great workaround for a missing box item.”
Liked products but found fasting boring by day five.
“we liked the products, however, and perhaps it's just us, by day5 we were just so bored with fasting, and wanted "food".”
David in customer service promptly replaced package and exceeded expectations.
“He went above and beyond by sending a complete new package without hesitation.”
Using HSA was difficult but eventually succeeded.
“Using my hsa was a real chore”
Service was described as helpful, informative, and cooperative.
“Helpful Informative Cooperative”
Reviewer says product is too expensive for limited incomes.
“The product is too expensive for persons with limited incomes.”
Results exceeded expectations without drugs or strict calorie counting.
“The results that I got were greater than my expectations.”
Customer was charged for three kits and cannot get resolution.
“Prolon charged me for 3 kits instead of just the 1 kit I wanted.”
Uses fast twice yearly and finds bars and shakes helpful.
“The bars are a healthy snack, the protein shakes are a great help”
Learning the "reset" concept changed the reviewer's health perspective.
“I learned about the concept of "reset" from Prolon,”
Enjoys five-day fast; never hungry and feels it's beneficial.
“I enjoy doing the 5-day fast with food.”
Reviewer found the website easy to use.
“Easy website”
Recurring orders arrive on schedule; reviewer satisfied with product quality.
“I find the products to be of high quality”
Appreciates 30% discounts and free shipping enabling fasting program.
“Always appreciate the 30% discounts & free shipping to allow me to do FMD.”
Charged more than expected; soups taste poor and organic option costly.
“I subscribed thinking each kit was $150, but on my 2nd shipment they charged $195 without notice.”
First Prolon experience was easier and tastier than expected.
“It was easier and tastier than I expected.”
Appreciates quality and quantity of communications and responsiveness.
“I appreciate the quality and quantity of communication from Prolon.”
Experienced hunger mid-fast but felt amazing by day five.
“And by day 5, I just felt amazing.”
Reviewer reports great customer service overall.
“Great customer service”
Package arrived timely; directions clear and foods tasted good.
“Package arrived in a timely manner.”
Online shopping promotions and discounts were confusing and inconsistent.
“The online shopping experience is inconsistent and confusing.”
FMD reset preferences, reducing cravings and improving food choices.
“It's a complete reset for my brain to switch on my preference for good healthy food over unhealthy food choices.”
Customer service helped obtain the proper soups and was amazing.
“Thank you for helping getting the proper soups. Customer was amazing!”
This page combines submitted experiences with public reviews from platforms such as Google, Trustpilot, etc. Recurring points are summarized without changing the content of reviews.
Fast Bar makes nutrition bars and related meal products for people doing short-term fasts or using meal replacements. It sells both kits and individual items through an online store. Shoppers can order once or sign up for recurring deliveries on the website. Fast Bar ships bars, shakes, and multi-day kit items to customers and takes online payments.