Does Synephrine Help You Lose Weight?

Does Synephrine Help You Lose Weight?

There are literally hundreds of plants, remedies and supplements out that that are reported to help you achieve your weight loss goals. The problem is of course that some work better than others- and some just don’t work at all.

Synephrine is a popular supplement on the weight loss market, with many brands choosing to include it as part of their fat burner ‘stack’ of ingredients. You’ll also see it included on these supplements by the names bitter orange and citrus aurantium.

Many of these supplements claim to promote healthy weight loss as well as support optimal physical performance- but many people don’t currently understand how or even if it works.

Here we discuss why this nutrient may not be the best choice for your weight loss goals- and may even be unsafe.

Read more to find out:

  • What is bitter orange?
  • What is it used for?
  • The Science- does it help with weight loss?
  • What are the potential adverse effects and interactions?
  • Final word

What is Bitter Orange?

The bitter orange tree can be found is many warm climate areas, but is originally native to Eastern Africa and parts South East Asia. It is a 10 meter tree when fully mature, with dark green leaves, white flowers and a vibrant orange fruit.

Alternative names for this nutrient include ‘citrus aurantium’, ‘C. aurantium‘ as well as the more common names ‘Seville‘ and ‘Sour‘ orange

What is Bitter Orange used for?

As a supplement, you’ll usually find it in fat burners and stimulants, and it’s typically marketed to promote the following benefits:

  • Weight Loss
  • Fat Burning
  • Increase in Energy and Performance

But it’s not just in supplements…

As a natural product, practically all parts of the tree are used in various medicines- this includes the leaf, flower and fruit.

Due to the bitter taste, the fruit is not usually eaten, however extract from the peel is used to flavor a range of foods and drinks (both alcoholic and non-alcoholic), as well as make the oil used in supplements.

Bitter orange is used in a number of products including aromatherapy, foods, medicines and cosmetics largely due to its reported anti-fungal, anti-inflammatory and bacterial properties.

Traditionally it has been used in Chinese and Amazonian medicine for a number of medicinal needs including stomach complaints, nausea, diarrhea and constipation. Additionally it has been used as treatment for skin diseases and some cancers, as well as anxiety and insomnia.

What the science says- does Synephrine help with weight loss?

So do these reported health benefits make it a potent fat burner?

The bitter orange plant contains many phtyochemicals– these are the biologically active compounds found in plants that provide nutrients and color [1].

The fruit contains a number of organic compounds, but the main one is the stimulant synephrine, or p-synephrine– similar in structure to ephedrine [2] and ephedra.

The alkaloids in this nutrient have been reported to increase energy expenditure, decrease appetite and increase metabolism therefore has been implicated as a weight loss supplement as well.

So that sounds promising right?

Well, not really– as with a lot of these compounds, research is limited so its effects have not been repeatedly tested under strict conditions. Much of the research that has been conducted has been privately funded too [3]. This makes it difficult to look at research results objectively.

The most comprehensive study to date [4] which analysed all existing research on this nutrient, demonstrated no statistically significant benefit for weight loss, and provided limited information about safety either.

Key Points:

  • You will find bitter orange as a supplement ingredient as p-synephrine or C. aurantium. 
  • At present there is just not enough scientific evidence to support the use of bitter orange for any health purposes- including weight loss.
  • The small number of benefits reported have been by privately funded studies. 

Side effects and adverse reactions

Firstly its worth mentioning that taking amounts found naturally in food are unlikely to cause many side effects- but due to the fruit being so bitter, its unlikely that you’ll be able to eat it.

However, issues start to arise when you are taking concentrated amounts as found in supplements containing synephrine. 

Remember that it’s also chemically similar to both ephedrine and ephedra- both banned by The U.S. Food and Drug Administration. This is due to links with blood pressure, heart attacks and stroke, and it’s also banned by the National Collegiate Athletic Association (NCAA) due to affects on health.

There are a number of case reports and studies that have reported negative effects of synephrine supplementation.

  • Study 1:

One case [5], a report of a previously healthy 24 year old man, found that using a fat burner containing the ingredient caused a STEMI- essentially a heart attack caused by a thrombus in his coronary artery, within hours of usage… 

…and this was someone who had NO risk factors for coronary artery or heart disease! 

  • Study 2:

Likewise, another study [2] reported a case where a 38-year old woman suffered a stroke after using another synephrine-containing supplement for one week. Again, she had no previous history or risk factors. The study concluded that using supplements of this kind could cause ischemic stroke in healthy individuals.

Interactions with other supplements and drugs

This nutrient is typically used alongside a number of other ingredients and rarely in isolation. For this reason it is important to be aware of potential interactions.

For example, one case [6] involving a 52-year old woman, reported the emergence of unremitting tachycardia rapid heart rate without cause, after taking a dietary, bitter orange extract-containing supplement (500mg, synephrine 30mg per day) alongside long-term thyroid medication.

Caffeine- Similarly to ephedrine, it appears to be especially dangerous when taken alongside caffeine according to the German Federal Institute for Risk Assessment (BfR) [7]-

Many bitter orange supplements contain a combination of synephrine and caffeine and therefore may not comply with current regulations- this could classify them as unsafe.

Other side effects-

As well as the very serious side effects of heart attacks and strokes here are a number of other side effects:

  • Diabetes– It may negatively effect blood sugar meaning that if you are diabetic you need to use with caution and monitor your sugar levels closely.
  • Irregular heart rate– you should avoid it if you have an irregular heart rate as it may cause ‘arrhythmia’ particularly when combined with caffeine.
  • May effect the ability of the skin to protect from UV rays- this makes you more susceptible to sunburn.
  • It may cause headaches and migraines- particularly if you suffer from cluster headaches or migraines with aurae.

Key Points: 

  • Both ephedrine and ephedra are banned by The U.S. Food and Drug Administration
  • There are a number of reported side effects and interactions associated with this nutrient

Does Synephrine Help You Lose Weight? Summary

  • This nutrient has little evidence to support its role as a weight loss supplement and the only research to claim this was privately funded therefore had compounding interests.
  • When taken as a concentrated supplement it has been linked to a number of illnesses including heart attack, stroke, high blood pressure and a number of other acute illnesses.
  • Its chemical structure is very similar to that of both ephedrine and ephedra- both on the FDA banned substance list.
  • According to the BfR, the combination of synephrine and caffeine may not comply with current regulations- this may classify them as unsafe.

Is there a safer option for fat loss?

There is.

It’s important that you choose to use ingredients that are safe and also proven to work.

Instant Knockout is an industry-leading fat burner that helps you achieve fat loss goals by boosting your metabolism in a safe way. Using exhaustively researched ingredients, including cayenne pepper and green tea extract and a host of vitamins as well as many other nutrients.

It’s even been endorsed by multiple MMA fighterswho have seen benefits such as:

  • Increased Calorie Burning – Lose fat faster
  • More Energy – Stay motivated for longer during workouts
  • Appetite Control – Reduce food cravings and stay on strict diets
  • Day-Long Fat Burning – Multiple servings throughout the day

– Learn More About Instant Knockout –


  1. National Toxicology Program. Bitter orange ( Citrus aurantium var. amara) extracts and constituents (+/−) p-synephrine [CAS No. 94-07-5] and (+/−) p-octopamine [CAS No. 104-14-3] . Review of the Toxicological Literature. 2004 : 1-73
  2. Bouchard, NC. Ischemic stroke associated with use of an ephedra-free dietary supplement containing synephrine. Mayo Clin Proc. 2005; 80(4): 541-5
  3. Stohs, SJ et al. Effects of p-synephrine alone and in combination with selected bioflavanoids on resting metabolism, blood pressure, heart rate, and self-reported mood changes’. Int J Med Sci. 2011; 28(8): 295-301
  4. Bent, S et al. Safety and efficacy of citrus aurantium for weight loss. Am J Cardiol. 2004; 94(10): 1359-61
  5. Thomas, JE et al. STEMI in a 24-year old man after use of a synephrine-containing dietary supplement: a case report and review of the literature. Tex Heart Inst J. 2009; 36(6): 586-60
  6. Firenzuoli F et al . Adverse reaction to an adrenergic herbal extract ( Citrus aurantium ) . Phytomedicine . 2005 ; 12 ( 3 ): 247-248 .
  7. German Federal Institute for Risk Assessment (BfR). Health assessment of sports and weight loss products containing synephrine and caffeine. BfR Opinion No. 004/2013. Nov 2012