If you are about to choose a fat burning supplement then STOP. Read this article first. You must choose one that has the correct dosage and has clinical efficacy otherwise you will WASTE YOUR TIME AND MONEY. Here are the best fat bat burners for 2021
Diet pills, fat burners and the weight management products category as a whole is the most variable aspect of the supplement industry.
$66 billion dollars were spent on fat burners in 2021 in the US Alone – most of the products sold were under strength!
It’s variable in terms of the ingredients used, the efficacy of the products, the claims made, the bio-chemical pathways involved and the secondary effects that can occur.
Here are the best fat burning supplements that are geared towards weight management (or weight loss for want of a better word) and fat loss for muscle definition and cutting.
Fat burners are THE most common and popular form of diet pills – they are suitable for both men and women who want to lose weight or use a supplement (cutting cycle) as part of fitness or workout regime.
Ask a dozen people why they want to use a fat loss supplement and you’ll likely get a dozen different answers.
What to Look For in a Fat Burner
If you’re looking for advice on how to identify a good product, what to look for, and what to avoid, then this is the guide for you.
I’ll also highlight some of the industry’s best current ingredients, hopefully undercutting the inexperienced, and frankly incorrect, nonsense that pervades the internet.
The following list, we feel, covers the best product for each major reason for wanting to use a fat burning supplement.
#1 PhenQ – Most Effective Fat Burner for Men and Women
Who is it suitable for? Anyone who wants to lose body fat.
PhenQ is a great product. It is without gimmick, hype or hyperbole.
The people behind it have resisted the temptation to associate it with an ultra slim women in a bikini or an ultra fit ripped man in the gym – but make no mistake it is a powerhouse.
It has no celebrity endorsements, no catch phrase and no trendy new (largely useless) ingredients. And I absolutely love it.
Whether you need to lose weight or burn fat and retain the lean muscle mass PhenQ is ideal.
When I recommend this product I do so safe in the knowledge that customers will be buying a thoroughly researched product that offers value, is safe to use and will in most cases deliver what it promises.
PhenQ is a multi benefit diet product – what that actually means is that several mechanics of action are in effect.
It can do much more that just burn existing fat.
Most of the top products available have multiple benefits but PhenQ takes the concept to a new level.
- Fat Burner – contains Capsimax (capsicum, piperine, caffeine and niacin (vitamin B3)) A very effective thermogenic fat burning ingredient.
- Fat Blocker – blocks the potential for new fat by stopping the absorption of a percentage of the fat in your food from being digested by your stomach.
- Appetite Suppressant – stops the feeling of hunger, can prolong the feeling of satiety and reduce the need to snack
- Fight Fatigue / Tiredness – one of the biggest reasons why diets fail is the onset of fatigue and the need to snack on sugar laden foods
There is also a mild mood enhancing ingredient present. I must stress that the mood enhancing (nootropic) dosage is relatively small and is the only disappointing element of of the formula.
PhenQ has a 60 day money back guarantee. It is delivered all over the world (with a few notable exceptions) for free.
Bottom line – If PhenQ doesn’t help you lose weight it is highly unlikely anything else will.
#2 LeanBean – Female Fat Burner
Who is it suitable for? Women who want to lose body fat.
LeanBean is a fat loss supplement and appetite suppressant intended for women.
In truth though, there is not many reasons why men cannot use it – the pink packaging maybe a deal killer for a majority of men though.
The marketing of LeanBean is the exact opposite of PhenQ. LeanBean is Instagram, it’s Pinterest – it is a great looking brand and the people behind it know how to exploit demographic superbly.
The product itself is virtual perfection. It’s formulated and dosed correctly.
It is not just a fat burner though.
- Help to raise your metabolism and burn body fat. There is Turmeric and Cayenne Pepper to help boost your metabolism safely.
- Help to reduce cravings and suppress appetite using Glucomannan – arguable the most studied and cited hunger suppressant that has ever existed.
- Help to support your body’s natural balance with ingredients like Vitamin B and Green Tea
LeanBean has a 90 day money back guarantee.
#3 Instant Knockout – Cutting & Muscle Definition
Who is it suitable for? Anyone who needs a fat loss supplement for cutting body fat
Instant Knockout is squarely aimed at men and women who workout and want get a more chiselled and defined look.
It helps the fat loss process while preserving lean muscle mass.
It is ideal for virtually every physically active person: Bodybuilders, body conditioners, fighters, sportsmen, athletes.
It is manufactured by Roar Ambition, a company that sure knows how to promote their products – and why not they are responsible for some industry defining products.
Instant Knockout is distinctive due it fist shaped bottle and vivid red capsules. It is also distinctive by it’s use of some very good ambassadors:
- Pro MMA fighter Diego Sanchez
- The #1 MMA coach in the world, Greg Jackson
- John Dodson – one of the top MMA Flyweights in the world
Instant Knockout ….
- includes ingredients that are scientifically proven to work
- contains those ingredients at effective dosages
#4 Clenbutrol – Cutting Cycles / Stacking
Who is it suitable for? Anyone who needs a fat burning/cutting supplement. Great for stacking.
It’s probably a bit unfair to label Clenbutrol as number 4 as it has a specific target customer – namely the the bodybuilder/body conditioner (or someone who works out).
Clenbutrol is from CrazyBulk – it was brought to the market as an alternative to Clenbuterol – a substance that has safety and legality issues.
Clenbutrol burns fat and improves cardiovascular performance by increasing oxygen transportation, enabling users to burn fat while retaining lean muscle mass.
- Safe and Legal Clenbuterol Steroid Alternative
- Powerful Fat Burning
- Improves Muscle to Fat Ratio
- Preserves Lean Muscle Mass
- Provides a Ripped Physique
- Boosts Performance
- Enhances Stamina and Endurance
- No Needles or Prescriptions
- Delivers Results Within 30 Days
- Free International Shipping
What Are Fat Burners?
Fat burners mostly come in the form of capsule supplements now, though there are more and more powders (like fat-burning pre-workout supplements) hitting the market these days.
Some are expensive, some are dirt cheap. Most contain multiple ingredients in what is commonly referred to as a formula, while others contain only one compound.
There are stimulant based formulas and stim-free formulas, and certain inclusions can cause certain unwanted side effects.
A few of them even work. Most are a waste of money.
What every one of them is supposed to do, is reduce your quantity of body fat.
Fat burners are THE most popular and common form of diet pill and for anyone intent on losing weight.
They usually contain other ingredients that help with other areas of weight los such as: appetite suppression and fat blocking.
This is for both men and women who want to lose weight, improve their health and burn fat – for anyone not just gym bunnies!
Losing weight will improve your health and give you life longevity!
How Do Fat Burners Work?
There are a few ways in which they and the ingredients they contain can trigger the biochemical processes in your body that ultimately lead to more fat being “burned” as an energy substrate.
A term you will most likely have heard in conjunction with fat burners and the like is “thermogenesis”.
What Is Thermogenesis and Why Is It Important?
Thermogenesis literally refers to heat production. In the context of the human body, it is essentially a metabolism regulating mechanism.
It is the process of converting nutrient calories – either those being consumed or those stored – into heat energy for the purpose of maintaining homeostasis, i.e. a stable temperature (thermoregulation), healthy metabolic function and weight control.
In basic terms, the body’s basic form of energy – ATP (Adenosine Triphosphate) – is used up in order to oxidize fatty acids as rapidly as possible. This ATP utilization generates heat, hence the thermogenic effect.
Once the process of thermogenesis finishes, the cell switches back to synthesizing and storing ATP.
Much of this is driven by the stimulation of beta-adrenergic receptors and the actions of UCP1 (Uncoupling Protein 1). If you want to jack into some more detailed science about the process at the cellular level then I recommend reading this review by Stohs and Badmaev
Thermic Effect of Food
Eating isn’t a one way energy system. It provides you with fuel but digesting your food requires some energy input as well.
The heat that comes from this process is called the thermic effect of food (or feeding/eating). It’s a significant amount to as it makes up between 5% and 10% of your total daily energy expenditure (TDEE).
Exercise Energy Expenditure
You’re constantly utilizing energy or synthesizing its substrates and storing them. Your metabolic functions – those that keep you alive – are always using energy.
Exercise requires energy input above that, and again, the heat production from physical exertion needs no introduction as everyone has experience it.
Cold Exposure and Non Shivering Thermogenesis
As I mentioned, thermogenesis helps keep us warm amongst other things. When our external temperature drops below a certain point, our biological thermostat kicks into gear a process called non-shivering thermogenesis.
This involves a body tissue called Brown Adipose Tissue (BAT) or brown fat. It originates from the same stem cells as muscle tissue, and shares many of the same characteristics.
For one, BAT uses white fat (the body fat your want rid of) as fuel to increase body temperature. This activation of BAT is particularly useful when we are infants because, proportionally speaking, we have much more of it.
We also cannot shiver to generate heat when we are babies, so we rely almost wholly on BAT to warm us up.
As we grow older, our brown fat stores become less important but they still have an effect, and recent research shows that we can “brown” white fat cells to increase our stores of BAT.
What’s more, we can activate brown fat through intentional cold exposure or through the use of certain ingredients and supplements.
I’ll explain more about Capsaicin (capsicum/hot pepper) and Turmeric in a little while but these are two of the more powerful ingredients used to light up our BAT stores and torch unwanted white fat.
Cold exposure and diet induced thermogenesis are examples of adaptive thermogenesis. It’s one of the mechanisms that starts to fail in models of obesity.
Thermogenic supplements fit into this category as well, and their use has become extremely popular.
There are two basic categories of thermogenic fat burning supplements:
Stimulants are compounds which interact with the central nervous system (CNS) or the sympathetic nervous system (SNS).
A sort of over-arching rule is that to be called a stimulant, it must temporarily increase the activity or efficiency of the whole or part of an organism.
Many stimulants also have thermogenic effects because they interact with beta-adrenergic receptors. They should hence be referred to as thermogenic stimulants.
Caffeine Anhydrous is probably the supplement industry’s most utilized thermogenic stimulant. Ephedrine is one of the more potent compounds, which also happens to be banned in most places.
Synephrine is an example of a sympathomimetic. It is structurally similar to ephedrine but while it does have strong beta-3 and thermogenic effects, it doesn’t interact much with beta-1 and beta-2 receptors. As such it doesn’t have much of an impact on the CNS.
Thermogenic stimulants are popular because they have multiple short-term benefits in addition to fat burning, including improvements in energy, cognitive function and focus.
However, they can also have a few unwanted side effects, especially for people who are sensitive to them. Stimulants increase heart rate and can cause nausea, headaches, dizziness and a nervous energy commonly referred to as ‘the jitters’.
Stimulants can either bind directly to adrenergic receptors (e.g. b1, b2, b3) or they can influence them indirectly by boosting levels of noradrenaline (norepinephrine) and adrenaline (epinephrine) which then bind to the receptors themselves.
The most powerful stimulants do both. They trigger the increase of noradrenaline and adrenaline while also acting on the adrenergic receptors to induce further CNS effects and stimulate thermogenesis.
Non-Stimulant thermogenic supplements do not increase CNS or SNS activity but still work via beta-3 receptors and so can trigger a fat burning response.
Great examples are capsaicin, green tea, cayenne and turmeric and groups of ingredients include: flavanoids, isoflavanoids, polyphenols and carotenoids.
Perhaps the most interesting aspect of some non-stimulant thermogenics is their effect on brown adipose tissue and the ‘browning’ of white adipose tissue (WAT).
Effective Thermogenic Stimulants
There are a number of stimulants which induce thermogenesis and thus fat loss. Some have less of an impact on the CNS than others and therefore have less associated effects, such as increased heart rate.
Caffeine is the most common stimulant in the world, owing to the fact that it is found in coffee and tea.
It’s main action is to increase levels of cyclic adenosine monophosphate (cAMP) which is a key intermediary in the cellular energy cycle. In tissues where cAMP is increased (adipose, brain, muscle, organs) the efficiency and activity of that tissues increases.
One of caffeine’s mechanisms is to stimulate the release of CNS neurotransmitters, which further increases metabolic turnover, energy and cognitive function.
Make no mistake, caffeine is a potent ingredient but it must be used correctly in order to get the best results from it.
Habitual caffeine use (e.g. two/three cups of coffee per day) will lead to an insurmountable tolerance, where no increase in dosage will bring benefit (and will only increase negative side effects).
Once tolerance has set in, which can happen at around 8 to 12 weeks depending on the individual) it is best to reduce intake over a few days and then cycle off it completely for a couple weeks.
This will reset the body’s tolerance and allow it to once again feel the benefits.
For more information on caffeine, how to use it, how to cycle it and what it can do for you, click here
Yohimbine is a powerful molecule which acts as both a beta-agonist (activates bet-adrenergic receptors) and an alpha-antagonist (suppresses alpha-adrenergic receptors).
Beta-agonists include all of these thermogenic fat burners, whether they are stimulatory or not, because they trigger their effects through b1, b2 and/or b3 receptors.
The beta-adrenergic receptors are associated with lipolysis (breakdown of fats), whereas the alpha-adrenergic receptors suppress fat burning.
By acting as an antagonist on alpha receptors, Yohimbine basically blocks their suppressive effects on the breakdown and metabolism of fats.
Perhaps of most interest to people looking for a potent fat burner is the selectivity yohimbine has for alpha-2 receptors which appear to accumulate in the thigh area in women due to estrogen effects.
This means that yohombine could be one of the only one with the ability to effectively target stubborn areas of fat in women. More research is required to confirm this.
While it is a promising ingredient in the context of fat loss, yohimbine can induce anxiety in people who are predisposed to it.
It can even cause panic attacks in those susceptible. What’s more, yohimbine interacts with neurological medications, including certain anti-depressants.
Should you consider using yohimbine, it is wise to make sure you are not taking any medication with which it can interfere and if you suffer from anxiety, panic attacks or depression it is probably better to steer clear.
After checking all of that, if you are still up for it, then it is recommended to start with a very small dose in order to assess your tolerance level. When it is taken in conjunction with other stimulants, or even non-stimulant beta agonists the effects can be increased.
Effective Non-Stimulant Thermogenics
Some of these may still have a small effect on the CNS but the impact is negligible and so they cannot be considered stimulants.
Synephrine – Citrus Aurantium – Bitter Orange extract
Synephrine is a compound present in bitter orange fruits, otherwise known as Citrus Aurantium.
You may have seen, used, or heard of the industry standard branded extract called Advantra-Z.
It binds to the beta-3 receptors of cells which as explained above are those which trigger the breakdown of fats and their subsequent metabolism.
Interestingly, synephrine can also increase glucose uptake into muscle cells and increases glycogenolysis (breakdown of stored glycogen to glucose for energy use), gluconeogenesis (production of glucose from non-carb sources), glycolysis (breakdown of glucose) and even oxygen uptake.
Hesperidin and naringen are two citrus bioflavanoids that are often found alongside synephrine in multi-ingredient fat burners. They have been shown to enhance one another’s thermogenic effect.
Synephrine is also synergistic with caffeine, especially in people who have reset their caffeine tolerance.
Capsaicin – Hot Chili Pepper Extract
Capsaicin might be included in a fat burning supplement in the branded form called CapsiMax, which applies a special time-release coating the powdered chili pepper so that it gets to the right part of the intestine and has maximum effect.
The main bioactive compounds in hot red peppers are called capsaicinoids and capsiate, the former being pungent and the latter being non-pungent.
Most research has been carried out with capsaicinoids but capsiate has very similar effects.
Capsaicin can increase fat burning via the activation of BAT and the browning of WAT. The browning of WAT creates what has become known as ‘brite’ fat or beige fat – somewhere in between brown and white, in essence.
This process enhances the concentration of cellular mitochondria in an area of white fat and thus increases the fat loss potential.
Capsaicin also acts as an appetite suppressant and a vasodilator, i.e. the relaxing of the smooth muscle which lines the walls of blood vessels, allowing for greater blood flow and oxygen deliver.
The combination of all of these benefits makes capsaicin one of the must-have fat burning, and overall health, ingredients to look out for in a product.
Green Tea – EGCG
Green tea contains bioactive molecules called catechins, which include EGCG – or epigallocatechin gallate – the most abundant and possibly most potent of them.
A cup of green tea contains a moderate quantity of EGCG but a green tea extract standardized to a specific amount of the molecule, at a strong dosage, can do a lot more.
When included alongside caffeine, green tea works especially well because it actually inhibits the enzyme that degrades catecholamines (most notably norepinephrine/noradrenaline), which stimulants like caffeine trigger the release of.
By slowing the degradation rate of catecholamines, they can continue to stimulate the beta-adrenergic receptors and thus prolong the oxidation of fat.
Green tea can have this effect in isolation because it also contains caffeine, although the quantity can vary from one extract to another.
Most quality fat burning products will contain both a green tea extract, standardized to a quantity of EGCG, plus a caffeine anhydrous inclusion.
Turmeric and Curcumin
Curcumin is the active component of turmeric and has been shown [source] to induce the browning of white adipose tissue (WAT) whereby the cells develop more mitochondria, which can in-turn burn more stored fat.
Adding black pepper to turmeric increases its absorption significantly and the two ingredients should therefore always be included together.
Forskolin from Coleus Forskohli
Coleus forskohli is a herb which contains a bioactive compound called forskolin.
Forskolin indirectly increases fat burning activity by stimulating the release of cAMP but without stimulating the CNS to a noticeable degree.
Forslean is the most well known branded standardized extract of Forskolin.
Green Coffee Extract and Chlorogenic Acid
Green Coffee Bean extract has become a very popular weight management supplement and much of it is down to the initial successes of its main active component, chlorogenic acid, in scientific studies.
Chlorogenic acid is mostly associated with a reduction in glucose absorption from eating which results in weight loss [https://www.ncbi.nlm.nih.gov/pubmed/18035001].
However, other research [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3925247/] indicates that chlorogenic acid probably has a fat burning effect independent of the carbohydrate blocking.
Chlorogenic acid can inhibit the enzyme which deactivates cAMP, which results in an increase of AMPK.
AMPK (adenosine monophosphate activated protein kinase) is an enzyme which can be considered a metabolic lever – i.e. when it is activated it plays a central role in energy metabolism and homeostasis.
The metabolic lever is catabolic, and involves the breaking down of fats to be burned.
Green coffee bean extract is a multi-faceted fat burning ingredient which does not cause any negative side effects.
Many decent products contain a lot of ingredients these days. Some products have lengthy formulas on their labels, detailing all kinds of inclusions from mood boosters to physical appetite suppressants.
The products above are excellent examples of the best fat burners to buy.
But the essence of a good product, and arguably the most important ingredients they contain are thermogenic compounds.
The heat energy that these cause to dissipate from the body’s cells puts the “burn” into fat burner.
I’ve discussed how the process works, and introduced some of the best ingredients in the business.
Hopefully this article can help you choose the best fat burners and the best supplement that will work for you.
The main issue is that it’s a fairly unregulated business. Once a few basic rules are followed, pretty much anybody can design and manufacture a product they are allowed to call a dietary supplement.
As with any industry that has a long leash and short lead time on product release, the competition is fierce and the marketing is creative.
Exaggerated claims, pseudo-science and poetic license are all tools of the diet supplement company’s tradecraft.
Finding the solid ingredients and products amongst all of the advertising noise is therefore the responsibility of the buyer.
To that end, I want to highlight a few of the ingredients included in these products that can exert fat burning, or other weight management, effects on the user.
A Word on Dosage
Almost all diet pills these days are under-dosed, with the exception of certain cheap ingredients, which ironically are often present at stronger than necessary quantities.
Aside from the ingredient’s effect, dosage is the most important factor. A compound that has been proven to work at a certain dosage might be completely useless at much lower, and in some cases higher, quantities.
The point is: finding a proven ingredient’s name written on a product’s label is only half of the information you need.
Caffeine has a mixed reputation. It’s probably the most commonly used ingredient in diet pills and fat burners. As such it is thought by many to be over-used, and even used to create the feeling of an effect for the user.
In fact, caffeine is effective, provided it is used correctly. My main complaint with respect to caffeine is that it is sometimes the only ingredient of any real effect in a product, but is relatively cheap for the company to include. This makes it a go-to for them, in terms of profitability.
To use caffeine properly, it is important to understand one very important characteristic of the stimulant: it causes an insurmountable tolerance response.
Insurmountable tolerance means that once your body has become used to the ingredient, it loses its effect to the point that no increase in dosage will reinstate those effects.
This is the main reason caffeine is seen as a short term supplement, an over-hyped stimulants, or even an ineffective ingredient.
The tolerance thing is easily avoided, if you have the will power to use caffeine in the right way.
- Other sources of caffeine, coffee being the main one, should not be consumed while taking it in supplemental form (i.e. for the whole 8 to 12 weeks cycle – see below)
- Caffeine should be cycled. This means using it daily for 8 to 12 weeks before reducing the dose over the course of a few days, and then taking 2 weeks off caffeine completely.
- Once the two weeks has passed, the user’s tolerance will be “reset” and the cycle can be repeated.
A common mistake made with caffeine is that it is used habitually, especially coffee drinking, by most people. Drinking coffee daily ultimately leads to it losing any beneficial effect as described above.
Caffeine Anhydrous is the purified “extract” of caffeine. It allows the dosage of caffeine to be controlled precisely, and contains none of the other additional elements of a coffee bean.
Drinking coffee on the other hand makes for highly variable doses of caffeine.
Dosage is something which can be altered up or down over time, depending on a person’s ability to tolerate the mild side effects of caffeine.
It is commonly accepted that the maximum quantity one should consume within a day is 500mg, and that ought to be spread over 2 or 3 separate servings at different times.
Dosages as little as 75mg per day can work for some people, both for fat burning and the benefits to cognitive function.
Earlier, I talked about caffeine anhydrous and how it is one of the most common ingredients in fat burners. There’s good reason for it’s ubiquitousness, though. It works.
Caffeine is a stimulant, and other types of stimulants are also often found in fat burners and diet pills. Again, this is simply because they increase the rate at which fat is used as fuel.
Stimulants can also improve cognitive function, energy levels and in some cases testosterone production.
Forskolin – from Coleus Forskohlii
One of those ingredients, which can improve cognitive function, energy levels and testosterone production is Forskolin, a bioactive compound found in the herb Coleus Forskohlii.
Ingredients like caffeine and forskolin can increase levels of cyclic adenosine monophosphate – cAMP – which is derived from ATP (Adenosine Triphosphate), the major energy providing molecule in the human body.
When cAMP, itself a messenger, is present in elevated concentrations in different soft tissues and organs, it can increase certain processes within those areas.
Examples include the elevation of testosterone levels when cAMP concentrations are increased in the testes, fat burning is increased when it’s in fat cells, and cognitive function is improved when it occurs in the brain.
Synephrine – from Citrus Aurantium (Bitter Orange)
One of the original fat burning stacks was known as the ECA stack. That is Ephedrine, Caffeine and Aspirin in combination.
The modern equivalent of that, updated mostly because the newer version is much safer, is Synephrine, Caffeine and White Willow Bark (a source of salicylic acid).
Synephrine is often included in fat burning supplements within its parent extract called Citrus Aurantium, aka Bitter Orange.
Bitter Orange contains several active compounds but the one with most fat burning power is p-synephrine.
When p-synephrine is isolated and included in fat burners it has similar fat burning effects to ephedrine – another central nervous system stimulant.
However, synephrine does not raise the heart rate significantly (at recommended doses) the same way that ephedrine can, and is therefore considered a better option for losing body fat.
Nootropics – Mood Boosters – Cognitive Function Enhancers
These aren’t direct fat burners, generally speaking. Of course, the odd stimulant can improve mood and cognitive function, but nootropic ingredients are being added to weight management supplements more and more because they can genuinely help.
When you’re dieting, your state of mind and general mood is of utmost importance. It becomes even more important when you are exercising while also dieting.
Exercise itself can improve mood of course, but it can also increase the hunger pangs for something sugary and decadent.
Some products like bodybuilding pre-workouts and fat burners even include nootropic ingredients as the “sensorial” or “mood boosting” suite, and other similar names.
Adaptogens like Rhodiola Rosea, Ashwagandha and Panax Ginseng might be included to reduce the stress, and possibly anxiety, associated with dieting and calorie restriction.
When cognitive function ingredients are used in this way, they are a form of appetite suppression.
Keeping your mood positive and healthy during a period of calorie restriction is very important and can be assisted by one or more of these supplemental ingredients.
Specifically, Ashwagandha and Rhodiola are very interesting, and have more than one benefit to cognitive and physical health.
Losing weight through calorie restrictive dieting combined with exercise is by far the best and most efficient way of going about it.
The addition of a quality supplement can help your efforts by directly burning fat or helping you to tough it out mentally.
Diet pills and fat burners can only ever account for 200 to 300 calories a day, any significant amount more would be too difficult to control, and possibly even dangerous.
When combined with a healthy diet and exercise program. Those extra calories make a lot of difference.