Zinc is supposed to boost testosterone levels, support muscle building, drastically reduce the duration of viral infections, and now it is supposed to become a slimming agent? Well, contrary to appearances, the subject of the influence of zinc supplementation on the process of fat loss, although rarely raised, is definitely worth bringing up. There is scientific evidence suggesting that, at least in some circumstances, supplementation with this micronutrient may bring significant benefits contributing to faster loss of excess body weight.
The biological role of zinc
Zinc is one of the essential components of our diet and ensuring an adequate supply is crucial for maintaining a peak health state. The role played by this element in the human body is versatile. Zinc is a component of approximately 200 enzymes – factors driving biochemical transformations occurring in the body . Thus, directly or indirectly it takes part in almost all metabolic processes such as:
- protein synthesis, (including muscle proteins)
- hormone production (such as testosterone)
- immune response (protecting the body against infections)
- and many others.
But is there any reason to believe that additional supplementation of zinc can bring benefits in the form of faster fat loss?
It all started with ZMA
The history of zinc as an ingredient of dietary supplements for people wishing to improve body composition dates back to 2006, when Victor Conte, the founder of BALCO Laboratories and shareholder of the SNAC system, developed and released ZMA. The product was a combination of organic forms of magnesium and zinc supplemented with vitamin B6 and was claimed to significantly increase testosterone and growth hormone in men, thus contributing to improved exercise parameters, as well as to increased muscle tissue growth and intensified reduction of fat tissue. The first studies on football players, financed by the ZMA manufacturer and conducted among others by Victor Conte, showed that the supplement has some potential, but later studies effectively refuted these claims indicating that ZMA supplementation does not bring significant benefits in terms of increasing testosterone levels or improving strength and body composition [2; 3]. Thus, zinc’s interest has clearly dimmed from that time.
A new, promising perspective
However, the situation is likely to change. A year ago an interesting experiment was published that did not involve athletes but obese people with a sedentary lifestyle (BMI > 30; age: 18-40 years old) . In the cited study, participants of both sexes with obesity were divided into two groups:
- the first group followed a diet with an energy deficit of 300 kcal and took a zinc-containing 30mg of zinc (in the form of zinc sulfate)
- the second group followed an energy deficit diet of 300 kcal but took a placebo
Both calorie and macronutrient ratios in both interventions were similar (carbohydrate: 55%, protein: 15%, and fat 30% of energy).
Participants were required to complete 3-day ongoing note-taking diaries and a questionnaire to assess hunger and satiety states before the start of the intervention and during the last week of the study. Participants were also advised not to make changes in their usual physical activity during the study. The experiment lasted 15 weeks.
What did they find?
There were significant differences in weight loss between groups (-4.60 kilograms for group one, zinc supplement vs -1.48 kilograms for group two, taking placebo), BMI, waist (-5.12 vs. 1.49 cm), and hip size was more significant in the group taking the zinc supplement than in the placebo group. Importantly, the group receiving the zinc-containing supplement had lower levels of high-sensitivity C-reactive protein and apelin and lower HOMA-IR values than the control group. Additionally, participants receiving zinc sulfate also noted a positive effect of supplementation on appetite control.
The results of the above study are interesting in that, given current norms, the zinc intake among participants in their usual diet, assessed before the intervention, did not indicate the possibility of deficiency. Thus, it can be assumed that in the case of obese people, either for some reason the body’s demand is increased and additional supplementation leads to some, as yet poorly understood, effects that promote weight loss.
It should also be added that this was not the first study showing the benefits of zinc supplementation in people struggling with excess body weight .
Dietary sources of zinc
Is supplementation the only right choice? Well, in the cited study, the participants received a significant additional dose of zinc, as it was 30 mg per day (in addition, the subjects’ existing diet provided 14mg of this element). Obtaining such an amount from conventional food is difficult, but… possible. The main dietary sources of zinc are meat, liver, legumes, nuts, seeds, and cereals . Its content in food is as follows (data are given per 100g of edible parts of the product):
- calf liver: 8.5mg
- pumpkin seeds: 7.50mg
- pork liver: 4.5mg
- fatty gouda cheese: 4mg
- beef: 3-4mg
- buckwheat groats: 3.5mg
- almonds: 3.2mg
- pork: 2.5-3.5mg
- oatmeal: 3mg
- sunflower seeds: 2.7mg
The bioavailability of zinc present in the diet depends on many factors. Among others, it is increased by selected organic acids such as citric and malic acid and the presence of certain amino acids such as asparagine. Its bioavailability decreases with the presence of nonchemical iron, copper, oxalic acid, some fiber fractions, and with a very high intake of phytates (these compounds are present in whole-grain cereal products).
Usually, with a well-balanced diet, the average zinc intake ranges from 10 to 20 mg, which, according to accepted standards, does not entail any risk of zinc deficiency or excess. With an incorrect choice of food, the situation may look different. And it is important to remember the conclusions of the quoted work: additional zinc supply in obese people can be used as an element of actions aimed at reducing body fat.
On the other hand, careless and chronic supplementation with high doses of zinc is not a wise idea as it can contribute to:
- disruption of copper metabolism in the body
- impaired lipid metabolism manifested by a decrease in the level of “good” (HDL) cholesterol and an increase in “bad” (LDL) cholesterol.
Zinc is an essential component of our diet. Adequate zinc intake is essential for the body to maintain a peak health state, and there is reason to believe that zinc deficiencies may cause, among other things, a decrease in immune resistance and lower testosterone production. Additionally, what is particularly important for people struggling with excessive body weight, zinc supplementation (in the amount of 30 mg per day) may significantly accelerate the reduction of fat tissue. The effect of zinc supplementation noted in the study was more significant than those observed in the case of classical weight loss supplements.
. Roohani. Zinc and its importance for human health: An integrative review. J Res Med Sci.18(2):144-157. (2013).
. Brilla, Conte. Effects of a Novel Zinc-Magnesium Formulation on Hormones and Strength. Journal of Exercise Physiology Online. 3 (4): 26–36. (2006)
. Wilborn. Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism”. Journal of the International Society of Sports Nutrition. 1 (2): 12–20. (2004).
. Khorsandi. Zinc supplementation improves body weight management, inflammatory biomarkers and insulin resistance in individuals with obesity: a randomized, placebo-controlled, double-blind trial. Diabetol Metab Syndr 11, 101 (2019).
. Payahoo. Effects of Zinc Supplementation on the Anthropometric Measurements, Lipid Profiles and Fasting Blood Glucose in the Healthy Obese Adults. Advanced pharmaceutical bulletin. 3. 161-165. (2013).