Can Supplements Block Fats?
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Can taking a pill actually block the fat you consume in your diet?
If you’re trying to lose weight, the idea of a fat-blocking supplement might seem intriguing. Fat blockers—
a sub-genre of fat burners—reduce how much fat you absorb from your food. Some fat blockers inhibit the pancreatic enzyme lipase, which breaks down fat—or lipids—in the food you eat into parts small enough to be digested. When lipase can’t do its job, the fat can’t be absorbed. Other fat blockers bind to the fat molecules and directly prevent it from be absorbed. But do fat blockers really work? And if they do, do the benefits outweigh the risks?
Types of Fat Blockers. The best-known lipase inhibitor is orlistat, which is available by prescription as Xenical or over-the-counter as Alli. When taken with a meal, orlistat prevents the absorption of about 25 percent of the fat consumed from that meal.
Another widely available fat blocker is chitosan, a fibrous sugar that comes from the outer skeleton of shellfish. It’s marketed as a dietary supplement for lowering cholesterol levels and supporting weight loss—often being billed as a “fat trapper.” Humans can’t digest chitosan, and once it’s in the intestines, it can theoretically inhibit lipase and bind to fat from food, helping prevent fat absorption.
Some “fat burner” supplements include high amounts of fiber, including soluble fiber, which dissolves in water, forming a viscous gel that bypasses digestion, and may also reduce the amount of fat absorbed from food. However, while increased soluble fiber intake may help lower cholesterol, research is less supportive of its role in preventing absorption of fat or as a means of weight loss. In fact, some studies found that increasing soluble fiber as part of a low-fat diet may lower fat absorption, but increasing soluble fiber while eating a high-fat diet may increase fat absorption.
Effects on Body Weight. If you successfully reduce how much fat you absorb from your food, does this result in actual weight loss? It might, but it might not be much.
“Most research indicates that fat blocking supplements will help dieters achieve initial weight loss, however they aren’t always an effective tool for maintaining weight loss for the long haul,” says Kristen Smith, MS, RD, LD, registered dietitian at Piedmont Healthcare in Atlanta and a spokesperson for the Academy of Nutrition and Dietetics. She said that compared with other types of weight loss medications, fat blockers will likely result in the least amount of weight loss.
She also pointed out that even when fat blockers work, they aren’t a magic pill. As with any weight loss medication, fat blockers are designed to be in used in conjunction with other behaviors such as regular physical activity. “While it might appear that a fat blocker supplement is an easy tool for weight loss, it’s important that the other lifestyle interventions are also taking place at the same time,” she says.
One fat blocker that doesn’t live up to hype—at all—is chitosan. Early research studies suggested that chitosan was better than a placebo, but larger, better-designed studies that followed found that chitosan appeared to be ineffective at lowering body weight or cholesterol. The Federal Trade Commission has brought deceptive advertising charges against multiple dietary supplement companies.
Nutritional Considerations. Some of the vitamins in the food and supplements we ingest are water soluble, while others—vitamins A, D, E and K and beta carotene—are fat soluble, meaning they are transported and absorbed in the intestines in a way similar to fat. So, if you block fat absorption, you may be blocking the absorption of these nutrients, too.
Smith says it’s recommended that anyone taking a fat blocker should take a multivitamin that includes the fat-soluble vitamins to ensure that their nutrition needs are met.
Side Effects. Fat blockers are notorious for producing unpleasant side effects in some users. For example, people who take orlistat may experience a number of side effects, including stomach pain, loose or oily stools, difficulty in controlling bowel movements, and gas with oily spotting. Serious side effects that warrant an immediate call to your doctor include nausea, vomiting and loss of appetite, weakness, hives, and yellowing of the skin or eyes.
Chitosan’s side effects can include upset stomach, constipation and gas. People who are allergic to shellfish might also be allergic to chitosan, and it’s unclear if it’s safe for use during pregnancy or breastfeeding. It may also increase the blood thinning effects of warfarin and reduce absorption of acyclovir (Zovirax), which is used to treat symptoms of chickenpox, shingles, and herpes.
“When choosing a weight loss tool, fat blocking supplements may be harder to comply with due to some of the side effects such as loose bowel movements and flatulence,” Smith says.
Bottom Line: One of the functions is to prevent the absorption of fat, once the dieter stops the supplement the weight will likely return. “Fat blockers aren’t right for everyone. If you aren’t eating a high-fat diet the fat blocker might not be the right supplement for you.”
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