Obesity and its associated complications, such as type 2 diabetes, hypertension, and cardiovascular disease, represent a significant global health challenge. Dietary supplements, accessible to the general population, are often considered an attractive alternative or complementary approach to traditional weight loss therapies. Among these, fiber supplements, particularly those containing psyllium husk (the main ingredient in Metamucil), have gained attention for their potential role in weight management.
Understanding Fiber and its Impact on Weight
Dietary fiber, generally referring to indigestible carbohydrates found in fruits, vegetables, nuts, and grains, plays a crucial role in overall health. A high-fiber diet has been associated with a lower risk of certain cancers, heart disease, diabetes, stroke, and all-cause mortality.
One proposed mechanism for the benefits of dietary fiber in weight management is appetite suppression and an increased feeling of satiety. High-fiber foods are bulky and require more chewing, which likely leads to an improved feeling of satiety.
Metamucil: A Closer Look
Metamucil is a fiber supplement made from psyllium husk, a compound derived from the seeds of Plantago ovata. It is a type of soluble fiber, which means that it absorbs water and forms a gel-like consistency as it passes through the digestive tract. Metamucil is often used to support digestive health, lower cholesterol levels, reduce appetite, and improve blood sugar control. It also helps promote regularity by trapping water in the intestines, easing the passage of stool from the body. It’s available in powder, capsule, and wafer form and can be purchased over the counter without a prescription.
Psyllium Husk: The Active Ingredient
Psyllium husk is a popular dietary fiber supplement widely used as a gentle bulk-forming laxative and probably best known as the main ingredient in Metamucil. Psyllium is a natural, predominantly soluble fiber that forms a viscous gel when hydrated and is not digested or fermented. In the small intestine, psyllium gel increases chyme viscosity, slowing the degradation and absorption of nutrients. Psyllium husk supplements are a concentrated hit of soluble fiber that have been studied extensively and been proven to help lower cholesterol, relieve constipation and diarrhea, regulate blood glucose levels, and treat GI issues.
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Clinical Studies on Psyllium and Weight Loss
Several studies have focused on the potential weight loss effects of Metamucil and psyllium. For instance, one 2018 study in 51 people with type 2 diabetes found that supplementing with psyllium decreased constipation, blood sugar levels, and body weight, compared with a control group. Another, older 2016 study observed similar findings, noting that psyllium improved blood sugar control and decreased body mass index (BMI) in 40 people with type 2 diabetes.
A 2019 critical review showed that the addition of psyllium improved blood lipid profiles, glycemic response, and increased satiety.
A meta-analysis of six clinical studies evaluated the effects of psyllium on body weight, BMI, and waist circumference in overweight and obese participants. The meta-analyses showed that divided doses of psyllium (before meals, 7-15 g/day, mean 10.8 g/day; duration 2-12 months, mean 4.8 months) resulted in statistically significant reductions in body weight (−2.1 kg, p < .001), BMI (−0.8 kg/m2, p < .001), and waist circumference (−2.2 cm, p < .001).
Psyllium's Impact on Satiety and Appetite
Some research also shows that psyllium may help reduce appetite and increase feelings of fullness, which may be beneficial for weight loss.
Two sequential clinical trials investigated the effects of psyllium (Metamucil) on satiety. In Study 1, all 3 psyllium doses resulted in directional or statistically significant mean reductions in hunger and desire to eat, and increased fullness between meals compared to placebo, with both higher doses better than placebo or 3.4 g. The 6.8 g dose provided more consistent (p ≤ 0.013) satiety benefits versus placebo. In Study 2, a significant (p ≤ 0.004) decrease in the 3-day mean hunger and desire to eat, as well as an increase in fullness for psyllium relative to placebo was observed.
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Psyllium Husk as an Affordable Alternative
Called “the poor man’s Ozempic,” psyllium husk is enjoying a rise in interest as an affordable alternative to semaglutide. Psyllium husk can induce the same feeling of fullness as it contains more fiber than barley, beans, legumes, oat bran, and some fruits and vegetables. A single teaspoon of ground psyllium husk provides nearly 8 times more soluble fiber by weight compared with oat bran.
Dosage and Administration
Recommended dosages for adults suffering from constipation and IBS range from 3.5 grams to 7 grams mixed in 8 ounces of water 1-3 times daily. For patients using psyllium husk for weight loss, it’s important to note that this supplement should be used in addition to a healthy diet and regular exercise.
Potential Side Effects and Precautions
Psyllium husk is considered safe but does have laxative effects. Potential adverse effects include gas, bloating, and abdominal cramps. Advise patients to follow the directions on the package and drink at least 6 to 8 glasses of water daily when taking psyllium husk. Patients with trouble swallowing, or esophageal or GI issues, should not take psyllium husk and those with kidney disease should speak with their health care provider before using the supplement.
The Importance of a Holistic Approach
However, despite these potential benefits, Metamucil or similar fiber supplements shouldn’t be used as a primary weight loss product. Instead, try to increase your intake of soluble fiber through foods like fruits, vegetables, and legumes.
For patients using psyllium husk for weight loss, it’s important to note that this supplement should be used in addition to a healthy diet and regular exercise.
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Other Dietary Fibers and Weight Loss
Common nondigestible carbohydrates (NDCs) in dietary supplements are glucomannan, inulin, psyllium, and β-glucans.
Glucomannan is a natural dietary fibre composed of β 1,4-linked D-mannose and D-glucose monomers derived from a tuber called Amorphophallus konjac. Its mechanism of action for weight loss may be based on its ability to absorb 50 times its weight in water volume, causing delayed gastric emptying along with a feeling of satiety.
Inulin is a soluble, nonviscous, fermentable dietary fibre. Some studies suggest that inulin may promote weight loss in obese, dyslipidaemic individuals with cardiovascular risk factors. However, the most consistent finding in the literature is the ability of inulin to lower the concentration of triacylglycerols (TAGs).
β-glucans are soluble, viscous, gel-forming dietary fibres, which increase the viscosity of the dietary pulp to slow nutrient absorption and improve glycaemic control and the lipid profile. In addition, beta-glucans are readily fermentable; fermentation results in the loss of the gel- and water-binding capacity.
Dietary Fiber Supplements and Energy Restriction
One study investigated the additive effects of a combination of energy restriction (ER) and four dietary supplements on changes in the anthropometric and biochemical parameters in 100 overweight or obese participants who were randomly assigned one of the dietary fibre supplements containing different dietary fibres or a placebo for 8 weeks. The results confirmed that fibre supplements plus ER significantly (p < 0.01) reduced the body weight, body mass index (BMI), fat mass, and visceral fat and ameliorated the lipid profile and inflammation at 4 and 8 weeks after the start of the study, while in the placebo group, significant differences in some parameters were observed only after 8 weeks of ER. A fibre supplement containing glucomannan, inulin, psyllium, and apple fibre was the most effective at reducing the BMI, body weight, and CRP (p = 0.018 for BMI and body weight and p = 0.034 for CRP compared to placebo at the end of the intervention).
Personalized Responses to Fiber Supplementation
One study showed that high fiber consumption led to a rise in gut-bacteria-derived bile acids, which break down cholesterol and other lipids, and that there was a decrease in certain lipids.
Like arabinoxylan, inulin supplementation also seemed to affect certain groups of bacteria, depending on the dose. But at the highest dose of inulin, 30 grams, most participants experienced a spike in inflammation throughout the body. And for three participants, the increased inulin seemed to trigger a spike in an enzyme called alanine aminotransferase, a sign of liver damage.
Every participant had a unique, or outlying, response to supplementation.