Bitter Orange For Weight Loss

Last updated October 25th 2014

Bitter orange is just one of many fruit extracts in the weight loss market. This article will look at what it is, any studies and side effects associated with it, as well as safer alternatives.

An increasing amount of weight loss products use fruit extracts which make products sound more appealing as consumers are arguably more familiar with fruits, and using them implies that they’re more natural and good for you. Bitter orange is just one example of these fruits where its high concentration of unique compound ‘synephrine’ gives the ingredient its metabolism boosting reputation. This article will look closely at bitter orange, discussing its weight loss claims, searching for any relevant studies to back the claims up, as well as study the ingredient’s history of adverse side effects and investigate any safer alternatives available.

What Is Bitter Orange?

Bitter orange is perhaps more commonly known as ‘citrus aurantium’ when referred to in a medical sense. Bitter orange is a plant and its peel, leaf, juice and the fruit itself are used for both medical purposes and in cosmetics. For example, bitter orange oil can be made from the peel and is used in food as a flavouring agent, as it is in marmalade and liquors. The oil is also used in pharmaceuticals, cosmetics and soap. The peel can also be dried and used as a seasoning.

Furthermore, it’s used to treat stomach ache, nasal infections, chronic fatigue syndrome, intestinal ulcers, constipation, headaches, diarrhoea, faecal blood, prolapse and intestinal gas/flatulence. The oil produced and bitter orange itself also purifies and regulate fat levels in your blood, lower blood sugar, and stimulate the heart to improve circulation. It’s also used to treat liver/gallbladder disorders, kidney/bladder diseases, insomnia and anaemia, and it’s also applied to skin to treat inflammation of the eyelid. Bitter orange is said to improve appetite, but there are also claims that it can promote weight loss through its high concentration of ‘synephrine’, and it supposedly aids in boosting your metabolism, subsequently burning fat and encouraging weight loss.

What Claims Does Bitter Orange Make About Weight Loss?

Bitter orange makes multiple claims of promoting weight loss; primarily, bitter orange is known for its metabolism boosting properties, although there additional claims of fat burning and promoting satiety.

Bitter orange is both a metabolism booster and a fat burner, and the fruit extract targets these areas together, meaning that by targeting one of these areas, it will subsequently target the other. Bitter orange contains a number of alkaloids which are also known as ‘adrenergic amines’; these include, N-methyltyramine, hordenine, octopamine and tyramine. Out of these alkaloids, synephrine is said to be responsible for encouraging weight loss in bitter orange, or citrus aurantium.

All of these alkaloids trigger thermogenesis, which is how they boost metabolic rate and burn fat. Thermogenesis is a natural process that occurs in the human body whereby internal body heat is raised through alkaloids such as those present in bitter orange, particularly synephrine. By increasing the body’s heat, it uses stored fat cells for energy. This therefore increases energy levels, boosting metabolic rate and speeding up the process of burning fat, resulting in fat loss.

As well as thermogenesis, synephrine also encourages fat burning and metabolism boosting in another way; the alkaloids target different types of ‘receptors’, and it’s said that synephrine attaches itself with beta three receptors. This supposedly provokes the release of a fat burning hormone called catecholamines which causes lipolysis because it releases the enzyme ‘adenylate cyclase’. This speeds up the process of burning fat as well as boosting metabolism.

As said before, the alkaloids in bitter orange target different receptors; synephrine targets alpha one receptors. These are responsible for suppressing the appetite as they stimulate the stomach and send signals to the brain, tricking it into thinking you’re full and subsequently reducing calorie intake and therefore encourages weight loss.


Is There Any Evidence To Support These Claims?

Study one: ‘Citrus aurantium as a thermogenic, weight-reduction replacement for ephedra: an overview.’ (Study here)

This 2002 meta-analysis by Preuss HG et. Al. discusses the popular use of the thermogenic/appetite suppressing ‘ephedra’ in weight loss. However, they’re looking at how citrus aurantium/bitter orangecould replace ephedra.

They looked at 3 studies; the first was conducted in 1999 by Cocker et. Al. which was double-blind, randomised and placebo-controlled. Participants were either assigned a supplement consisting of citrus aurantium, caffeine and ‘St John’s Wort’ or a placebo pill, though both groups were put on a strict diet and exercise regime. Results showed a significant reduction in body weight for those taking the citrus aurantium supplement compared to the placebo group.

Another study by Jones used a smaller sample of 9 women over 2 weeks; the first week showed a mean average reduction of 0.94kg in combined body weight when they weren’t taking anything, and then a mean reduction of 2.40kg in the second week after using the citrus aurantium supplement.

Preuss HG et. Al. concluded that at present, citrus aurantium may be the best thermogenic alternative to ephedra, but more evidence is needed to make an accurate decision.

Study two: A 60day double-blind, placebo-controlled safety study involving Citrus aurantium (bitter orange) extract. (Study here)

This 2013 study was conducted by Kaats GR et. Al. who began their analysis with a brief summary of what bitter extract is and what it’s generally used for. The aim of their study was to examine the safety of bitter orange and the design was double-blind and placebo-controlled. The method involved a sample of 25 ‘healthy subjects’ who were split randomly into three groups, each receiving a different supplement twice daily for 60 days; the first group were given bitter orange extract on its own with roughly 49mg of synephrine, the second group were allocated the same but it was combined with naringin and hesperidin, and the third group were given a placebo pill. The results weren’t particularly conclusive but they showed that all three groups saw no significant difference in systolic/diastolic blood pressures, blood chemistries or blood cell counts, but all groups saw a slight difference in heart rate. They concluded that no adverse side effects occurred in any of the groups, and judging by their measurements, bitter orange and synephrine are safe to use in dosage of up to 98mg a day over 60 days.

Study three: A review of the human clinical studies involving Citrus aurantium (bitter orange) extract and its primary protoalkaloid p-synephrine. (Study here)

This is a meta-analysis looking at the results of various human studies that have been conducted on bitter orange. It was released in 2012 and was written by Stohs SJ et. Al. and the full version is available here. Their study looked at over 20 clinical trials which consisted of roughly 360 participants in total, over 50% of whom were overweight or obese. 44% of all participants took the bitter orange product alone, while the rest had a combination of different ingredients, and over all studies these products were taken for up to 12 weeks. Results generally showed that products containing bitter orange/synephrine either alone or with other ingredients showed an increase in metabolic rate, energy expenditure and in weight loss, and these results became visible when consumed for 6-12 weeks. Also, there weren’t any adverse side effects with any of the products, although this may be because the concentrations of bitter orange/synephrine are lower, and they concluded that more evidence is needed to produce more solid results.

What Side Effects Are Associated With Bitter Orange?

Contrary to rumour, bitter orange has an infamous reputation of causing adverse side effects. This may be surprising to some consumers as bitter orange extract/citrus aurantium became famous by arguably becoming the ‘safer alternative’ to the ingredient ‘ephedra’ which was banned in 2004 by the FDA. Results from clinical studies have also given people a valid reason for assuming bitter orange is a safe ingredient, with few results of side effects. However, this may just be due to the low concentrations of bitter orange used, and the short length of time in which it was used for as most studies examining the safety of the extract aren’t long at all. It’s said that although bitter orange appears to be safe for consumption for roughly 12 weeks, there doesn’t seem to be any evidence to suggest how it can effect you when it’s consumed for any longer length of time.

In actual fact, there are lots of sources that discuss the potential health risks associated with bitter orange/citrus aurantium and synephrine, the main alkaloid within the fruit. According to its WebMD page, there are multiple side effects possible when consuming bitter orange within medicine. They claim that it’s likely to be safe when consumed by both children and adults as a food, and when applied to the skin as an oil, and even when being inhaled during aromatherapy. Likewise, they suggest that it should be safe if consumed by pregnant women, if they’re using it for the purposes mentioned before.

However, the risks and problems are caused when the bitter orange is consumed for medical purposes, and they specify in particular when it’s used in supplements for weight loss, which is becoming its common use now. They say that adverse side effects of bitter orange are generally caused when people consume the ingredient with other stimulants such as caffeine. Examples of possible side effects when combining bitter orange with other stimulants include increased blood pressure, irregular heartbeat, headaches/migraine, fainting, heart attack and stroke, amongst others including seizures and intestinal conditions such as faecal blood, diarrhoea, vomiting, fever and abdominal pain/cramps. Allergic reactions to bitter orange may also occur, and signs of this include rashes, itching, hives, inflammation/swelling and the difficulty to breathe or swallow.

WebMD advise that due to the lack of clinical evidence, women who are pregnant or breastfeeding should avoid consuming bitter orange for medical purposes. More specific warnings imply that patients with type-2 diabetes should approach bitter orange with caution as it may interfere with blood sugar levels, and people suffering from glaucoma should also avoid it as it’s said to worsen the condition. They also advise that you stop taking bitter orange 2 weeks before any planned surgery because it could interfere by increasing heart rate and blood pressure, and they warn that it causes sensitivity to the sun.

It must also be noted that common side effects of synephrine include increased blood pressure, cardiac arrhythmias, flushes, sweating, irritability, respiratory problems, dizziness/headaches, tremors and blood sugar imbalances.

Bitter Orange Alternatives

As many more people are using bitter orange extracts for medical purposes including weight loss, the risks are higher, especially in prolonged and excessive use. This may turn many consumers off, steering them away from weight loss products that include this ingredient, especially if it’s combined with other stimulant ingredients such as caffeine, as many of them are. Therefore, this section will look at possible alternatives to bitter orange, specifically looking for ingredients that make the same claims of having thermogenic properties, boosting metabolism, burning fat and suppressing the appetite, just with fewer health risks attached but possibly more effective.

What Are The Alternatives To Bitter Orange?

When looking for an alternative ingredient to something you should pick out the key elements of the ingredient to try and find others that possess the same properties. In this case, we should look for a natural ingredient which has claims of fat burning, metabolism boosting and appetite suppressing, but with fewer risks of side effects. There don’t seem to be any ingredients that consist of synephrine which makes it difficult to find a very similar alternative, although it’s also what makes bitter orange so harmful, which is arguably a good thing.

Ideal alternative ingredients will be both thermogenic and appetite suppressants. Garcinia cambogia may be a good replacement as it both burns fat by blocking a fat producing enzyme called citric lyase and it suppresses the appetite by increasing serotonin levels. However, it doesn’t boost metabolim. Both green tea and African mango claim to target all three areas of weight loss, possibly being the best substitutes. Alternatively, any of these ingredients may be effective if combined with caffeine, as caffeine’s a natural metabolism booster and is often used in weight loss products to support other ingredients.

Are Bitter Orange Alternatives As Effective In Terms Of Weight Loss?

Bitter orange still isn’t a hugely well-known ingredient, and the alternatives mentioned are arguably more highly credited in the weight loss industry. This could be because they’ve had more successful reports, or they may have lower risk of experiencing and adverse side effects.

Green tea and African mango are both more well-known than bitter orange, but this doesn’t necessarily determine whether they’re more effective. Our article looks at green tea in closer detail, showing that green tea claims to burn fat, boost metabolism and suppress the appetite. This is because of its main ingredient ‘epigallocatechin gallate (EGCG)’ which is said to be a thermogenic catechin, meaning it increases body heat and uses stored fat cells for energy, which both burns fat and increasing energy levels/metabolic rate. Green tea also contains caffeine which also increases energy and improves exercise performance, but it also alters levels of the hormone ‘serotonin’, which stimulates your stomach and sends signals to your brain to make it think you’re not hungry.

Similarly, African mango acts as an appropriate alternative to bitter orange as it also targets all three areas of weight loss. African mango, or, ‘irvingia gabonensis’ claims to burn fat, boost metabolism and suppress the appetite. It burns fat by removing cholesterol from the body; the seeds are high in fibre and therefore reduce cholesterol levels and the fruit also slows down your digestive system, prolonging the absorption of glucose into the body meaning that the blood sugar levels can remove cholesterol, removing unwanted fats from the body. It boosts metabolism because the fruit encourages cells to release ‘adiponetin’, a hormone which supports metabolic rate and fat burning. It suppresses the appetite because of the slowed down digestive system which means food will stay in the body longer which will make you feel fuller and reduce cravings.

Both alternative ingredients have adequate explanations detailing how they contribute towards weight loss, but it’s important to look for clinical evidence to support the claims. Green tea has several clinical studies which show that some studies have resulted in positive weight loss, whereas other people less so, implying that more evidence is needed and it depends on the quantities taken. African mango has also had a clinical study which implied that although irvingia gabonensis did have successful weight loss, it may work better with other ingredients, but overall there’s a sufficient amount of evidence on both substitute ingredients.

Are Bitter Orange Alternatives Safer Than Bitter Orange?

In terms of the safety of the suggested bitter orange alternatives, neither green tea nor African mango have a reputation of adverse side effects like bitter orange and synephrine do. However, the side effects still exist and although they may not be as dangerous or as highly associated with the ingredient, it’s still worth knowing about them before consuming them so that you’re warned.

Green tea perhaps possesses more risks than African mango, as it contains caffeine; much like bitter orange, green tea has main ingredients that are responsible for its weight loss abilities. In green tea, the main ingredient is the EGCG which contributes towards thermogenesis, but it also contains caffeine which helps boost metabolism and increase energy levels. However, caffeine is the second main ingredient in green tea, whereas synephrine is the main ingredient in bitter orange.

According to WebMD, green tea is usually safe in moderation for short term use, although it may cause minor unpleasantries such as discolouring of the teeth, constipation and stomach ache, with more serious risks including damage to the liver.  Other risks are because of the caffeine and vary in severity, and include headaches, anxiety, insomnia, diarrhoea, vomiting, irritability, irregular heartbeat, nausea/dizziness, heartburn, tremor, ringing in the ears, convulsion and confusion. However, green tea contains much less caffeine than coffee and when used as an ingredient in a weight loss supplement, the concentration should be too low to experience any serious effects.

In contrast to green tea, irvingia gabonensis is a considerably new ingredient in the weight loss market, so there isn’t much evidence available to prove whether it’s completely safe or not. Most people have said it’s safe for use, and WebMD say that it’s ‘possibly safe’ for adults, though there have been a small amount of reports noting mild side effects such as flatulence, headaches and sleep problems. Although there’s a considerably low risk of experiencing adverse side effects from irvingia gabonensis, it’s still important to be cautious.

As mentioned previously, other alternatives could include garcinia cambogia or guarana combined with caffeine, and although this may be effective it would also cause higher risk of side effects because of the caffeine; in green tea, the concentration of caffeine is much lower than if it were on its own, and so it would almost be as dangerous as bitter orange, perhaps even more. However, it’s safe to say that green tea and African mango are much safer than bitter orange.


In conclusion, bitter orange makes some promising claims in burning fat, boosting metabolism and suppressing the appetite because of its main ingredient synephrine which targets different receptors. There’s in depth detail on how bitter orange does this which implies that it’s accurate and logical, and clinical evidence supports that bitter orange can have successful weight loss effects, but further evidence is required. The ingredient is brought down by its reputation of adverse side effects; although clinical studies show that it’s a safe extract in small quantities over a short duration and because it’s considered as ‘safer alternative to ephedra’, there are serious health risks attached and can interfere with different treatments and conditions. For this reason, it would be advised to either use this ingredient for short-term use only in moderation after consulting your doctor, or look for an alternative such as green tea or African mango.