Weight loss supplements are a big industry; many are marketed as fat-burning, metabolism-boosting, or appetite-suppressing, but there is no evidence to support these claims. Some supplements, such as protein powders and fiber, may support weight loss when paired with other lifestyle interventions, but most others offer little to no benefit. 

1. Fiber

Fiber is known to slow digestion and can support satiety. Some studies have shown that high-fiber diets and fiber supplements can help weight loss, though others have shown no benefit, such as:

• Supplements may not offer the same benefits as food: Studies suggest soluble fiber (fiber that forms a gel) supplements have mixed results on total calories consumed. While supplements have the potential to increase a satisfied feeling of fullness and decrease total calories eaten, more research is needed to understand the best types and dosages.
• The type of fiber matters: Soluble fiber may slow digestion and increase satiety, which could facilitate weight loss. One large analysis suggests that guar gum has the greatest potential for decreasing energy intake, but results have been mixed.
• A calorie deficit is still required: Fiber supplements may help weight loss paired with energy restriction. Because fiber can support satiety, some people may be able to maintain a calorie deficit to facilitate weight loss.
  

It’s recommended that adults consume 25 to 35 grams of fiber per day. It’s best to get fiber from food such as whole grains, fruits, vegetables, and legumes, which also offer other health benefits. However, if you cannot get enough fiber through your diet, a fiber supplement—when paired with a balanced diet and exercise—may help with weight loss. 

2. Calcium and Vitamin D

It’s been hypothesized that vitamin D and calcium supplements may facilitate weight loss. However, there is insufficient evidence to support this theory.

• Vitamin D: Low vitamin D levels have been associated with higher body fat levels. Researchers have looked at whether vitamin D supplements may lead to weight loss. While some studies have shown very small amounts of weight loss (1 to 2 kilograms) when paired with a calorie deficit, other research suggests no benefit. The National Institutes of Health (NIH) concludes that vitamin D does not help people lose weight. 
• Calcium: It’s thought that calcium may positively impact fat metabolism, which may lead to less fat storage or, potentially, even fat loss. Calcium and vitamin D together may support weight loss in specific populations.. However, conflicting research exists.

There isn’t enough evidence to back the benefits of vitamin D or calcium supplements for weight loss for everyone. However, it’s essential to ensure you are consuming adequate amounts of both for overall health. 

3. Probiotics

Emerging research suggests a more diverse gut microbiome (gut bacteria) is associated with lower weight, as follows:

• Probiotics can help you maintain a diverse gut microbiome. However, much is still unknown about the most important strains and the benefits of consuming supplements rather than eating probiotic-rich food. 
• Data show minimal benefit to taking probiotics for weight loss. Some studies have shown that supplements may lead to relatively insignificant weight loss (less than 1 pound).

More research is needed to understand the potential benefits of probiotic supplements for weight loss and, if there is a benefit, which strains and doses of probiotics are recommended. Prioritize foods and drinks rich in probiotics, such as yogurt, kefir, kimchi, sauerkraut, and kombucha, to support a diverse microbiome.

4. Iron

Iron status and weight may be related, but more research is needed to understand how this relationship works and whether iron supplements help with weight management.

• Iron deficiency is associated with obesity: Observational studies suggest a connection between higher body weight and iron deficiency. This could be due to how iron is metabolized, related to diet and access to iron-rich foods, or other factors such as inflammation that could impact iron levels. Some small studies suggest weight loss may support better iron levels, but more research is needed.
• Iron deficiency can cause fatigue: Fatigue is a common symptom of iron deficiency anemia, which can cause people to become less active. Since exercise is an integral part of weight management, there could be an indirect link between low iron and weight.

There is a lack of substantial evidence in humans to suggest that iron supplementation helps with weight loss. However, if you’re deficient in iron, it’s recommended to prioritize iron-rich foods and consider supplements to ensure adequate levels. 

5. Protein

Protein plays a role in appetite regulation and muscle growth and maintenance, both of which can support weight loss, as follows:

• Protein helps you feel full: Protein supports fullness by slowing digestion and impacting hunger hormones. High-protein diets have been shown to support satiety and weight loss in the short term, though more studies are needed to understand their sustainability and impact on weight beyond 12 months.
• Protein helps build muscle mass: When paired with resistance training, protein can help you maintain and even build muscle mass. Maintaining muscle mass is essential to supporting your metabolism, which may help with weight loss and maintenance.
• High-protein diets may support weight loss or prevent weight regain: Although there is no agreed-upon definition of a high-protein diet, studies show that consuming more than your Recommended Dietary Allowance (RDA) (0.36 grams per pound of body weight, g/lb), even double the amount (0.73 g/lb), can reduce fat and maintain lean muscle mass. High-protein diets may also help prevent weight regain.

Protein powders alone will not necessarily lead to weight loss, but they may be an effective supplement for helping you meet higher protein recommendations. 

6. Caffeine

Caffeine—found in coffee, tea, and supplements—has long been explored as a tool for weight loss.

• It may not be an appetite suppressant: Some diets may suggest coffee to suppress appetite. However, studies show this is not an effective weight loss approach and may not even impact food intake or appetite.
• You may develop a tolerance to caffeine: The National Institutes of Health (NIH) states that weight loss supplements with caffeine may support short-term weight loss, but you can develop a tolerance to it, which can lessen the impact over time.
• Caffeine supplements may not be safe: The FDA has warned against taking high doses of pure caffeine in the form of supplements as it can lead to serious side effects, including erratic heartbeat, seizures, or death. The NIH states that up to 400 to 500 milligrams (mg) of caffeine is safe for most adults, and many supplements contain higher amounts.

While some small studies have shown that caffeine could support weight loss, others have shown no benefit, and supplements with caffeine can lead to nausea, vomiting, rapid heartbeat, and other, more serious side effects.

7. Green Tea Extract

Green tea and its extract, EGCG (epigallocatechin gallate), have been explored as possible weight loss aids, but the evidence doesn’t suggest many benefits, as follows: 

• The effects of green tea extract are small: Although some studies have shown that green tea extract may contribute to weight loss, the effect is minimal. For example, one study found that taking a high dose of EGCG in the form of green tea led to less than 1 kilogram of weight loss over 12 weeks. It’s unknown if that weight loss is maintained and for how long. The consensus is that green tea extract is not an effective tool for weight loss.
• Safety is important to consider: According to the NIH, green tea is considered generally safe at up to 8 cups per day. However, the safety limit for EGCG supplements (green tea extract) has not been established. One study suggests that healthy adults could safely consume up to 338 mg of EGCG per day. Other studies have found much higher doses have minimal benefits.

Green tea and green tea extract are not effective supplements for weight loss. 

8. Bitter Orange

Bitter orange is a common ingredient in weight loss supplements. It contains synephrine, which is a stimulant that some supplement companies claim can burn calories and fat. Evidence includes:

• Bitter orange and synephrine don’t lead to weight loss: Research on bitter orange and synephrine is relatively thin, and studies are low quality. One meta-analysis of 18 studies showed that bitter orange does not lead to significant weight loss.
• Bitter orange may not be safe: It can lead to chest pain, anxiety, increased heart rate, high blood pressure (hypertension), and muscle and bone pain.

Between the safety concerns and the lack of data supporting bitter orange for weight loss, it is not recommended as a supplement for weight management.

9. B Vitamins

B vitamins play a vital role in energy production and metabolism, which has led to exploring their role in weight. Research reveals:

• B vitamin deficiency is associated with higher body mass index (BMI). However, it’s unclear if the relationship is causal in either direction—meaning B-vitamin deficiency contributing to weight gain or higher weight impacting absorption and metabolism—or if it is associated with other factors.
• Small studies in animals suggest supplements may increase metabolism. This relationship has not been shown in humans. 

There isn’t any evidence to suggest that taking B vitamins helps with weight loss. However, if you have a B vitamin deficiency, supplements can help you replenish your levels, which is essential for overall health. 

When to Contact Your Healthcare Provider

Before starting any new supplement, discussing it with your healthcare provider is recommended. However, it’s essential if you: 

• Take any medications: Supplements may interact with medications and make them more or less effective. 
• Have underlying medical conditions: Supplements may exacerbate certain medical conditions, so ensuring a supplement is safe for you is essential. 
• Take other supplements: Supplements can interact with each other, and too much of any one nutrient or ingredient may not be safe. Always review all of your supplements with your healthcare provider to determine what is safe for you.

Supplements are not risk-free, even if marketed as “natural.” Always discuss any supplements you’re taking or considering taking with your healthcare provider or a registered dietitian who can evaluate your individual situation.