Weight loss is primarily caused by a caloric deficit created through dietary restriction (i.e. eating fewer calories than you burn). The next most powerful factor in weight loss, coming in at a distant 2nd, is energy expenditure caused by exercise (i.e. burning calories through physical activity). Dragging far behind both dietary restriction and exercise is energy expenditure caused by the consumption of weight loss supplements. Despite impressive marketing claims, supplements do very little to promote weight loss [1,2,3].
Understanding the Role of Supplements
The limitation of a weight loss supplement can be found right in its name. “To supplement” means “to add, enhance, or offer a finishing touch”. A cherry enhances an ice cream sundae, just like a supplement can enhance weight loss, but you certainly would not consider a cherry to be a significant portion of the sundae. Similarly, supplementation is not a significant consideration in weight loss, and it should be your last priority, if you choose to use supplements at all.
Weight loss supplementation is meant to optimize an already effective weight loss effort. If you don’t currently have a consistent and well-managed nutrition and exercise program, supplements will do nothing for you. It’s like modifying your car to make it more aerodynamic while the engine is broken. You can make all the superficial changes you want, but the enhancements to the car won’t help anything until the car’s fundamental components are working. At best, supplements can provide a minimal enhancement to your weight loss effort. Bear in mind that losing weight can happen effectively and efficiently without any supplementation.
Weight Loss Supplements, or just Caffeine?
To keep this article simple, I will focus on one of the most common active ingredients in weight loss supplements – caffeine . Many weight loss supplements boast a wide range of ingredients that allegedly promote weight loss. When reading through the ingredient lists of such supplements, you will commonly find several exotic-sounding herbal extracts, but you can safely assume that caffeine is present, even if it is not explicitly stated. In weight loss supplements, caffeine often masquerades behind caffeine-containing substances such as: coffee bean extract, tea leaf extracts (black, green, and white), kola nut extract, guarana, and yerba mate [4,5,6]. The reason why caffeine is so prevalent in weight loss supplements is because it is effective, albeit in a very mild way .
The Physiological Effects of Caffeine
Many of the substances found in weight loss supplements have little to no evidence to support their effectiveness [1,2,3], but caffeine does cause tangible effects . Caffeine is a stimulant, and its consumption stimulates the sympathetic nervous system (SNS), leading to an increase in blood pressure, heart rate, heart contractility, respiratory rate, resting muscle tone, and thermogenesis. Increasing each of these physiological functions requires energy, leading to an increase in energy expenditure (i.e. more calories burned). However, the actual amount of extra calories burned is minimal.
Caffeine also causes a “trick” physiological effect. Caffeine consumption inhibits the release of anti-diuretic hormone (ADH), which is an endocrine hormone that limits the amount of water that is filtered out of the bloodstream by the kidneys. If you decrease the body’s ability to retain water, you will urinate more, leading to a decrease in body weight. However, simply peeing more does not mean you are losing fat, and water weight can be put on as quickly as it is lost. Due to the diuretic effect of caffeine, weight loss supplements may “trick” you into thinking you are losing fat when you actually are just losing water-weight. In instances like this, the weight scale “lies”.
The Associative Effects of Caffeine
At this point we know that caffeine causes two physiological effects on the body that relate to weight loss: a very mild increase in energy expenditure  and an increased rate of urination . Neither of these effects will promote fat loss to any significant degree. However, caffeine consumption can potentially cause some associative effects that may promote weight loss more than its direct physiological effects.
As stated previously, caffeine causes an increase in blood pressure, heart rate, heart rate contractility, respiratory rate, resting muscle tone, and thermogenesis. These changes occur because caffeine stimulates the release of the stress hormones cortisol and epinephrine [8,9]. Both of these hormones contribute to the “fight or flight” response, making you feel more alert and energetic, and this is why caffeine is associated with feelings of jitteriness, anxiety, and motivation. Some individuals may seek to express these “fight or flight” feelings by exercising, or exercising more intensely than they usually do, which both lead to an increase in energy expenditure (the 2nd most powerful factor in weight loss). There is also evidence suggesting that caffeine consumption can suppress appetite [10,11], encouraging a reduction in caloric intake (the most powerful factor in weight loss).
Note that caffeine consumption does not literally cause you to exercise more or eat less, but rather it is associated these behaviors, hence the term “associative effects”.
Marketing Tactics & Supplement Industry Regulation
Questions: If weight loss supplements don’t make much of a difference in weight loss:
- Why are they on the market?
- Why do they cost so much?
Answers: Because they are sold by people who:
- Want to make a profit
- Know how to effectively market their products by making bold, unsubstantiated claims that appeal to the insecurities and desires of individuals who wish to lose fat
Caveat: The above statement is a generalization. As mentioned in the introduction of this article, supplements can provide a mild benefit only when used in conjunction with dietary restriction and increased physical activity. However, supplement marketing tactics are typically not aimed at individuals who already have an effective weight loss plan, but rather at uninformed and disempowered individuals looking for a quick, effort-free fix.
We live in a consumer society where the promise of instant gratification is one of the most effective marketing tactics. Consequently, many Americans are conditioned to desire and expect things that happen quickly and with little effort. However, the internal biological process of fat-loss has stubbornly stayed put while the external world has changed rapidly due to the progression of technology, for better or for worse. Not only does modern American society undermine healthy eating, which has resulted in an obesity epidemic, but it also provides false promises of easy weight loss with the help of a pill.
With clever and dishonest advertising, supplement companies can make large profits by selling products whose effects don’t match up to their cost. The supplement industry is loosely regulated, which allows for supplement companies to make unsubstantiated claims about their products.
Current supplement regulations, which are dictated by the Dietary Supplement Health and Education Act of 1994, allow for:
- Significantly reduced pre-market safety assessments of supplements 
- The FDA is not required to test new supplements before they are put on the market, meaning that the burden of determining the safety and effectiveness of supplements is put on the consumer and not the supplement companies.
- Loose restrictions on how supplement companies can make claims about their products, resulting in a large gray area of acceptable product claims 
- Companies can make claims based on their review of the scientific evidence about the substances in their products, encouraging dishonesty, misinterpretation, unreasonable extrapolation, cherry picking, and confirmation bias.
- Companies can make unsubstantiated claims as long as they abide by the following two conditions:
- 1. They don’t claim their products can prevent, treat, cure or mitigate disease.
- 2. They print the following disclaimer on their product labels: “This statement has not been evaluated by the FDA. This product is not intended to prevent, treat, cure or mitigate disease.”
Hierarchy of Factors that Affect Weight Loss
As stated in the introduction of this article, a caloric deficit caused by dietary restriction is the most important factor in weight loss, followed by energy expenditure caused by exercise, and lastly energy expenditure caused by supplementation. However, there is not an equal difference of effectiveness between these factors. For example, physical activity is not 50% as effective as dietary restriction, and supplementation is not 50% as effective as physical activity. The following metaphor will help explain the relative differences between the effectiveness of the three weight loss factors (i.e. dietary restriction, exercise, and supplementation).
If money can “buy” weight loss (meaning the more money you spend, the more weight you lose), dietary restriction is a 100 dollar bill, exercise is a 20 dollar bill, and supplementation is a 1 dollar bill.
- Dietary restriction + exercise + supplementation [$100 + $20 + $1 = $121]
- Dietary restriction + exercise [$100 + $20 = $120]
- Dietary restriction + supplementation [$100 + $1 = $101]
- Dietary restriction [$100]
- Exercise + supplementation [$20 + $1 = $21]
- Exercise [$20]
- Supplementation [$1]
In the above hierarchy, notice that the difference between level 1 and level 4 is not that large, but that the difference between level 4 and level 5 is profound, and that level 7 is practically negligible. As you can see, the presence or absence of dietary restriction is what makes the biggest impact on weight loss, and supplements provide no benefit when used on their own. Dietary restriction is such a powerful factor that significant weight loss can occur without the inclusion of exercise or supplementation.
- A caloric deficit caused by dietary restriction is the most powerful factor that affects weight loss, followed by energy expenditure caused by exercise, and lastly energy expenditure caused by supplementation.
- Significant weight loss can be achieved through just dietary restriction, but the same cannot be said for the isolated use of exercise or supplementation.
- Weight loss supplements are only effective when used in conjunction with an already effective nutrition and exercise program.
- Even when used appropriately, weight loss supplements only provide a very mild benefit.
- One of the most common active ingredients in weight loss supplements is caffeine .
- Caffeine is a stimulant that causes an increase in metabolic rate, albeit in a slight way .
- Caffeine causes a diuretic effect on the body , which may falsely lead someone to belief they are losing fat when they are actually just urinating more.
- Caffeine can suppress appetite [10,11].
- Caffeine consumption is associated with increased physical activity and decreased caloric intake.
- Weight loss supplements are frequently marketed with unsubstantiated claims that appeal to the insecurities and desires of individuals who wish to lose fat.
- Current federal regulations severely limit the pre-market safety assessment of supplements and place the burden of determining the safety and effectiveness of supplements on the consumer and not the supplement companies .
- Despite their minimal effectiveness, weight loss supplements are commonly used [13,14].
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