Updated May 8, 2019.
Published Apr 7, 2014.

FenFast is one of many products that aims to mimic certain aspects of Phentermine, an amphetamine-like prescription medication that is used as an appetite suppressant. This particular product claims it can cut your daily calorie intake in half. In reality, this is not much more that a caffeine pill. Anyone who is sensitive to stimulants will be subject to an array of side effects. FenFast is extremely expensive too, and there is no money-back guarantee if you buy it.


  • None whatsoever


  • Inadequate ingredients profile – you do not know the quantities
  • Expensive – $64 for a pill mainly containing caffeine
  • No money-back guarantee
FenFast 375 is an over-the-counter weight loss supplement that the makers claim will cut your calorie intake by 50% each day. This sounds good but will this Phentermine inspired diet pill really work and more importantly is it safe?

We take a look at FenFast 375 to find out.

FenFast Overview

What you need to know about FenFast

FenFast 375 contains some stimulant ingredients that may help increase the speed of your metabolism. Although this may help to give you some added energy and help you burn off fat, stimulants do cause side effects that may be unpleasant.

Hordenine works on your adrenaline levels and may make you feel too stressed to eat and not everyone can cope with high doses of caffeine. DL Phenylalanine lacks any clinical evidence that it does anything at all and the long-term safety effects are unknown. A major problem with predicting the effects of this pill is that we do not know the ingredient amounts. You will not really know exactly what you are taking.

What are the side effects of FenFast?

Side effects can oocur as a result of the stimulants included in FenFast, e.g. nausea, jitters, anxiety, increased heart rate and blood pressure, and heart palpitations.

How much does FenFast cost?

FenFast is expensive. It costs $64 plus $14.99 shipping to a US address.

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FenFast Key Features

FenFast 375 comes from Intechra Health a US supplements company who specialise in marketing what they say are close copies of Phentermine. This one contains just three ingredients and according to the sales pitch will improve your mood as well as help you lose weight.

FenFast 375 is a diet pill that offers a legal alternative to prescription drug Adipex and with some great attention to detail, Intechra Health has even made the pills look identical to this Phentermine brand. With blue and white flecks and the numbers 375 these pills look just like the real thing but according to the FenFast advertising, are safe for everyone to take.

Phentermine and the various brand names such as Adipex and Ionamin are only available by prescription for serious cases of obesity.

FenFast Key Points

  • Manufactured by Intechra Health in the US
  • Each bottle contains 60 tablets
  • Some of the ingredients lack clinical proof that they work for weight loss

Not phentermine diet pillsIn the USA and some other countries around the world, Phentermine is still used for obesity and it can be extremely effective. However it can be additive and there is a very real risk of side effects and many countries, including the UK have banned Phentermine because of the health risks and potential damage to heart valves. Even in the USA, it is never supposed to be prescribed without the close supervision of a doctor.

If you have a real Phentermine drug in your possession without proof of a doctor’s prescription, you can face legal charges because it is a class 1V controlled substance with links to amphetamines.

FenFast 375 is not an illegal drug. Instead, it gets its stimulant effects from caffeine and Hordenine with the added addition of an amino acid believed to improve mood.

How to Take FenFast

To use FenFast take one capsule twice a day. Information is not provided but we suggest with breakfast and lunch. FenFast contains stimulants so should not be taken too closely to bedtime.

According to the sales pitch, FenFast 375 has five key features:

  • Powerful Appetite Suppression & Cravings Control
  • Doubled Energy Levels & Performance Enhancement
  • Amped Up Metabolism for Faster Fat Burning
  • Better Overall Mood & Motivation
  • Weight Loss Effects Similar to Phentermine & Adipex

TrimThin SRFenFast 375 is made by Intechra Health and is one of a range of Phentermine inspired diet pills. Other products include Phen Blue described as a “body sculpting formula with noticeable results after 72 hours” and Trimthin SR – a copy of a slow release Phentermine brand called Ionamin. We covered both these supplements in previous diet pill reviews but did not accept either of them onto our approved list.

FenFast Concerns:

  • Some of the ingredients lack information about safety
  • Customers may be duped into spending money on a caffeine pill
  • May cause a number of stimulant side effects

FenFast 375 is made in the USA and according to the information contains clinically proven ingredients. (Clinically proven sounds good but is one of those phrases that does not strictly mean anything.)

According to the product information, when combined with a healthier diet and more physical activity FenFast 375 will help your body to burn off fat and calories by boosting the speed of your metabolism. In addition, FenFast 375 is also supposed to improve your mood and mental energy making you more likely to have a positive attitude about losing weight.

What does FenFast claim to do?

According to FenFast 375 product information, the diet pill has three key features;

  • #1 Best Adipex Alternative
  • Lose 15 – 25 Pounds a Month!
  • Burn Fat24 Hours a Day

It works by;

encouraging the body to speed up its fat burning processes, resulting in more fat and calorie burned, even when you are at rest.

FenFast 375 is made in the United States with only the highest quality standards and ingredients.

According to the sales pitch;

FenFast 375 Tablets were scientifically developed to help dieters achieve their weight loss goals more quickly and easily by mimicking the benefits of top prescription diet drugs like Adipex and Phentermine.

Does FenFast work?

It may work for some people but results are unlikely to be long lasting and it may cause side effects.

There is not much customer feedback available but opinion seems to be divided between positive and negative opinion. Some people have lost weight by using in combination with dietary changes and exercise as recommended by the company. Others have felt no benefits at all.

The effects of stimulants will vary from person to person. Often the body soon becomes used to the effects and the energy buzz simply stops working, as does the weight-loss.

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FenFast Ingredients

FenFast 375 is a stimulant based diet pill and although Intechra health have provided information about the three ingredients, this does not include the amounts contained in each tablet. Therefore, we can only provide a general overview because we have no way of knowing exactly how strong it is.

  • DL-Phenylalanine: This form of the amino acid Phenylalanine is called DL Phenylanine and is a chemical form of this amino acid, which is manufactured in the lab.
    Although the FenFast information claims that DL Phenylalanine has “been clinically studied for any years to make sure that its impact on the body is well understood”, there is no evidence that the studies have reached any conclusion. There is no evidence it helps weight loss or depression and it requires further investigation for all these claims.
    Bizarrely a link to clinical evidence posted on the FenFast ingredients page to prove efficacy of this ingredient, refers to chromium Piccolinate which is not even in this supplement.

Source: WebMD article

  • 1,3,7-trimethylxanthine: More commonly called caffeine and the principle ingredient in many so called fat burning diet pills. Some research has shown that caffeine can cause thermogenesis and fat oxidation (fat burning) and this can be helpful for weight loss.
    The clinical study referenced in by Intechra Health on the FenFast ingredients list was not conclusive. 136 people (some of them obese) were tested over a 3-month period. Some people lost weight and others did not. The test concluded that there were;

considerable individual variations within the group with regard to the metabolic rate and thermogenic response to caffeine.

However, 30 seriously obese subjects did experience significant weight loss when caffeiene was combined with low calorie diet and exercise programme over the 3-month period.

Source: Online Source

  • Hordenine Hcl: Is a naturally derived chemical found in plants including barley and is an alkaloid in the Phenylethylamine class. It is a stimulant and a common ingredient for weight loss supplements because it is believed to affect the central nervous system and increase the metabolism.
    It does this by boosting your adrenaline levels to promote the fight or flight response. This can suppress your appetite by making you feel too keyed up to eat.
    Largely untested on humans despite some promising initial results Hordenine is known for increasing heart rate and blood pressure. We were unable to access the clinical proof provided by the website.

FenFast Side Effects

Some customers have reported side effects that tie in with taking high levels of stimulants.

It did not give me that boost of energy characteristic to Phentermine or the appetite suppressant effect. It also made me really irritable. That was probably because I couldn’t sleep at night


Upset my stomach and it made me feel jittery.

Other side effects may include

  • Nausea
  • Vomiting
  • Headache
  • Anxiety
  • Elevated heart rate
  • Increased blood pressure
  • Heart palpitations

According to the FenFast 375 advertising, you should avoid this supplement if you are sensitive to caffeine.


Avoid FenFast 375 if you are pregnant or breast-feeding. Do not take if you are sensitive to stimulants and caffeine. You may need to avoid drinking coffee and other products containing caffeine while you are taking the pills.
Do not take if you suffer from a heart condition or have high blood pressure and see your doctor if you are taking medication in case this pill causes drug interactions.

FenFast Customer Feedback

There are a few customer reviews and response has been mixed. Some customers have been pleased,

I found that FenFast was good, it was safe and had good results.

This lady combined the tablets with a healthy eating plan and exercise programme and enjoyed the boost to her weight loss.

Another customer said,

I definitely recommend this product! I’ve been able to lose and maintain. It definitely works like Phentermine. Just make sure you drink plenty of water!

Not everyone is as pleased,

It didn’t work like it stated in their add. It lasted a short time and upset my stomach and it made me feel jittery.


I had no physical change at all nor any feeling of any effect from product usage in one month. I lived and learned and do not recommend anyone waste their money as well.

FenFast Money-Back Guarantee

No money-back guarantee is on offer, so we do not advise you to buy a bulk order before you have tried this supplement.

Where To Buy FenFast

You can buy FenFast 375 direct from the product website.

One month’s supply of 60 tablets costs $64 plus $14.99 shipping to US addresses. You can make savings on larger orders. For example, 3 month’s supply (180 tablets) costs $149 and includes free shipping. 6 month’s supply (360 tablets) costs $279 and includes free shipping.

If you live outside of the USA, you will need to contact Intechra Health for details and shipping costs.

FenFast 375 is also on sale via One month’s supply of 60 tablets costs $59.00 and includes free shipping.

Watchdog Verdict

When you get behind the hype of the advertising, FenFast 375 looks fairly mediocre. It will not help you cut your calorie intake by 50% a day and it does not offer you value for money.

Intechra Health have not provided a full ingredients profile so you cannot know how strong this supplement is and it is highly likely that the principle ingredient is caffeine. Staying on stimulants for too long will not help you lose weight and can be bad for your health even if the principle ingredient is only caffeine the world’s favourite stimulant. We are also concerned about the other ingredients because they do not appear to have been researched for long term safety.

We like the fact that the company advise that you take this in combination with a diet and exercise programme but make no mistake. This diet pill is not a substitute for Phentermine when it comes to weight loss.

Although we agree that FenFast 375 is probably safer that Phentermine, this description of FenFast being a legal substitute is misleading.

FenFast 375 is just not good enough and at this price is certainly not worth the money. We have no other choice but to reject it.

How does FenFast compare to Phentaslim?

CriteriaFenFast ComparisonPhentaslim comparison
Clinically Proven Ingredients
Side Effect Free
Positive Customer Reviews
24/7 Support
Money-back Guarantee

Disclaimer: Our reviews and investigations are based on extensive research from the information publicly available to us and consumers at the time of first publishing the post. Information is based on our personal opinion and whilst we endeavour to ensure information is up-to-date, manufacturers do from time to time change their products and future research may disagree with our findings. If you feel any of the information is inaccurate, please contact us and we will review the information provided.

Have Your Say

7 comments on 'FenFast'

  1. It gave me a severe headache. Tried to take 2pills a day couldn’t handle the bitterness and headaches. Took 1 pill daily for month. Saw no changes and couldn’t handle side effects. Bought buy 3 get one free. Still have them. Sad can’t get your money back!

  2. I only took my first dose of 2 pills and within 2 hours I started feeling sick at my stomach. I’m afraid to try anymore. I was really sick. Just wish I could get my money back.

    1. It gave me a severe headache. Tried to take 2pills a day couldn’t handle the bitterness and headaches. Took 1 pill daily for month. Saw no changes and couldn’t handle side effects. Bought buy 3 get one free. Still have them. Sad can’t get your money back!

  3. I got this and was only able to use it for 3 days. The side effects were killer. Nausea, cranky, headache and just very fuzzy. Couldn’t concentrate to get anything done. I definitely had no desire to eat, so the part of me that wants to be skinny is pretty bummed out. If a pill makes me feel this bad I really have to consider how bad it is for my health. It was like taking some gutter nasty street drug. Ugh 🙁


  5. I had heard a lot in the news about companies who make generic brands of medications. I decided to look into this company as it claims to be an American company. That alone gave me pause, as if you are an American company why is it important to tout on about being so? I called the number listed on their web site, and they wanted personal information, phone number, address, etc. I did not give them either as I found this to be strange.

    I asked the girl point blank if she worked for the company or an outside source? Her reply; ” I don’t have that information.” You don’t know who it is that you work for? I then asked if I could speak to a supervisor, and was then again asked for my personal information so that a supervisor could contact me when one was available. Again I refused. I ran off and called back 10 min later to get someone who was rather rude. I asked to speak to a supervisor, and was told again that none was available. I asked the same question as before, and was told that they worked for an outside source. I asked where in the US this company was located and was only told Washington.

    I later went back to their site to find that they have an address in WA, but it’s not a real address per google maps, but a mail station. I personally don’t have any money tied up with this company, nor will I ever. I think it’s a fraud, and or not a US based company. Very secretive on where they are located, can’t speak to anyone who has any sense and know who they work for, or where they work. Be very leery of a company who sales drugs that can’t furnish any proof of being FDA approved. Should have asked this question, but I’m sure I would have gotten the standard, “I don’t know, or “I can’t give out that information.”

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