Supplements are commonly asked about by patients in an obesity medicine practice. Questions regarding their effectiveness, safety, and impact on weight loss can be tricky to answer, partly due to a lack of regulations and oversight and the lack (or bias) of available studies. While an in-depth dive on supplements would require a significantly longer conversation, what the ABOM expects of your knowledge base is more manageable.

A supplement is defined as an additional element taken in addition to normal dietary intake. It can include vitamins, minerals, herbs, etc., and is considered food, not a medication, by the Food and Drug Administration. Therefore, they are not required to go through an approval process for consumption; essentially, they are considered safe until evidence proves otherwise. Also, supplements cannot be overtly advertised for treating or preventing medical conditions, although manufacturers often find creative ways to skirt around this.

Generally speaking, supplements are safe to take. There are a few that have shown a lack of effectiveness with potential harm, which has prompted required disclaimers (e.g., HCG), while others have been completely banned (e.g., ephedra). In addition, some cause indirect harm by interfering with prescription medication absorption or interacting with prescription medications. Others may even increase the risk of hepatotoxicity. In fact, up to 20% of all acute hepatic failure is attributed to weight loss supplements, with green tea extracts and anabolic steroids being the most commonly tested culprits.

Concrete information that must be understood for boards includes a knowledge of the side effects associated with commonly used supplements and the mechanisms by which they are theorized to work. Fortunately, the board exam likely will not devote a significant proportion of questions to supplements. Therefore, I recommend knowing the common ones listed in the table below. Side effects of most supplements may include headache, nausea, and gastrointestinal distress (i.e., flatulence and diarrhea). However, some have unique, and therefore more testable adverse effects:

  • Raspberry ketones: burps and hiccups
  • Glucosinolates: goiter and hypothyroidism
  • Carnitine: fishy body odor
  • Green tea extracts: palpitations, anxiety, and potential hepatotoxicity
  • Yohimbine: anxiety, tachycardia, and cardiovascular events

Most obesity organizations would agree that no legal dietary supplement ingredient has demonstrated to be effective for weight loss, and these should not be recommended in place of other proven, effective therapies. However, patients often pursue these as an alternative due to the ease of obtainability (no required medical visits or monitoring) and a significant bias of available studies. For example, positive studies are more commonly published and touted by the media regardless of sample size, whereas studies showing a lack of efficacy often are tabled.

One final point to clarify is that functional foods are not considered supplements. These are foods that may have additional benefits beyond their nutritional value, with some of the more commonly used ones listed below:

  • Dietary fiber: This may increase the sense of fullness and marginally decrease percent body fat.
  • Prebiotics: Indigestible oligosaccharides may stimulate intestinal growth, promoting a microbiome conducive to weight loss.
  • Probiotics: Bacteria (i.e., lactobacilli) in yogurt, etc., may protect against unfavorable yeast/bacterial overgrowth.
  • Caffeine or green tea (not extracts): May reduce appetite, increase fat oxidation, and provide antioxidants.

Although numerous supplements are available on the market, the ABOM is likely to require only a reasonable amount of knowledge about the most commonly used supplements. For more information on supplements, the Obesity Algorithm, released annually by the Obesity Medicine Association, is a great resource.

Sample Question

A patient presents to her physician with concerns about supplements she has been taking. She was started on L-carnitine and green tea extract at the recommendation of an herbalist. However, since starting, she has noticed increased anxiety, palpitations, and a slight tremor. Both of these supplements theoretically work by affecting which mechanism?

A. Satiety

B. Carbohydrate metabolism

C. Blocking fat absorption

D. Increase in fat oxidation

Next Week: MC4R Deficiency

Upcoming: OSA and Monthly Knowledge Check

For more practice questions, check out the following:

  • Obesity Medicine Board Review Questions (2026): Qs 175, 205, and 297.
  • Obesity Medicine Practice Tests (2026): Qs 54, 131, 134, 172, 180, 205, 347, 400, and 412.

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