By: Harry G. Preuss MD, MACN, CNS
Professor of Biochemistry, Medicine, Physiology, & Pathology
Georgetown University Medical Center, Washington D.C. 20057

The title of this report has been my “battle cry” for a number of years. The bottom line is that the success of every clinical investigation depends to a great extent on the compliance of the volunteering subjects1. Many supplements that have been said to be ineffective based upon evidence from well-designed protocols that have been designated as such for no other reason than poor compliance — especially true in “weight loss clinical trials.”

In the case of the latter, volunteers have their own means to follow progress — the personal bathroom scale. When the scale does not indicate immediate success after a few days, the subjects then believe they have been placed in the placebo group and discouragingly take their pills inappropriately or even completely stop consuming them.

Let me give you an example derived from one of our earlier investigations2.

The Study

In a double-blinded, placebo controlled study (the most accepted type of investigative design), my research team compared body composition changes and blood chemistries between an active and placebo group. Anonymous questionnaires assessing protocol compliance were administered at the termination of the study to determine compliance status among participants taking either three grams of a soluble fiber or placebo under their usual lifestyle conditions for 60-days. This resulted in four groups in all: compliant and non-compliant in the active grouping, as well as compliant and non-compliant in the placebo grouping.

Why was this especially necessary here?

Despite the fact that many dietary fibers are well accepted as possessing multiple health benefits, humans for the most part universally avoid them like the plague. In this case, only 83 participants who were to consume either two capsules three times a day of the fiber supplement or placebo completed the study.

The compliant active and placebo groups (roughly 40 percent of their respective totals), unlike the non-compliant ones, consistently consumed the required six capsules a day 30-minutes before eating as determined by the questionnaire and subsequent post-study telephone confirmations.

Ignoring compliance and considering only differences between active and placebo groupings, there were no statistically nor clinically significant differences found in regard to body weight, body mass index, percent body fat, and fat mass. In other words, with a standard protocol where compliance was not given special consideration, the fiber had proven ineffective. However, corrections for compliance in both dosing and timing differences between the compliant and non-compliant treatment, as well as the other potential placebo groupings (both the compliant placebo and non-compliant placebo groups alone and combined), brought out statistically significant differences.

For example, over-placebo differences comparing the active compliant group to the combined two placebo groups were: percent body fat: –1.6% (P=0.002), scale weight: –3.9 lbs (P=0.002), and fat mass: –5.7 lbs (P=<0.001). Ingesting the supplement correctly was also associated with reduced total and LDL cholesterol. Suffice it to say, the findings reveal the importance of correcting for compliance in a weight loss study.

While non-compliance in clinical studies has destroyed the reputation of many useful supplements, this problem is also prominent in their personal use. Patients expect immediate success and readily slack off a prescribed regimen when disappointed. Thus, they in turn downgrade effectiveness when others inquire.

Another prominent example of non-compliance is present in the use of a leading, perhaps the most leading, dietary supplement for weight loss – Garcinia cambogia.

For the first couple of weeks of consumption, the perception of reasonable fat loss is often masked — countered by an initial response to retain water and increase muscle glycogen well known for this supplement3.  Therefore, I consistently warn patients not to give up initially with its use. Accordingly, failure should only be accepted when proper compliance is demonstrated.

If you don’t comply, don’t complain.

As a final point, dietary supplements like many well-established drugs even with full compliance do not work on everybody and should not necessarily be dismissed cavalierly for general use when individual failures occur.

To read Dr. Harry Preuss’ biography, awards & achievements, click here!

  1. Kaats GR, Preuss HG: Challenges to the conduct and interpretation of weight loss research. In: Phytopharmaceuticals in Overweight/Obesity Therapy, second addition. (Eds) D Bagchi, HG Preuss, CRC Press, Fl, pp 833-852, 2012.
  2. 2. Preuss HG,Bagchi D, Kaats GR: Konjac glucomannan dietary supplementation causes significant fat loss in compliant overweight adults,  https://www.researchgate.net/publication/283206713_Konjac_Glucomannan_Dietary_Supplementation_Causes_Significant_Fat_Loss_in_Compliant_Overweight_Adults.
  3. Preuss HG, Bagchi D, Kaats G, Perricone NV, Scheckenbach R, Clouatre DL: Garcinia cambogia: a valuable member of the fat loss pharmacy. The Original Internist   21:207-214, 2014.