Can Certain Foods Help You Burn More Fat?

Though food is supposed to be one of life's simple pleasures, few things cause more angst and confusion. It's no wonder why. We're constantly being told which foods we should eat to be healthy, which diets we should follow to be skinny, which preparation methods we should use to be safe, and which chemicals and contaminants in food we should shun to avoid illness. It's enough to give anyone indigestion.

If you're confused about what to believe, you've come to the right place. In "Coffee Is Good for You," I'll give you the bottom line on an array of popular diet and nutrition claims in a quick, easily digestible way. Research about diet and health rarely yields the equivalent of DNA evidence, which provides incontrovertible proof. All types of studies come with caveats. However, if interpreted properly, a body of research can allow us to make sound judgments about how believable a claim is.

To that end, I've carefully reviewed the relevant studies and assigned each claim to a category on what I call the Truth Scale:
  • Good Evidence: This means the claim is believable because there's solid supporting evidence from at least several randomized trials or large cohort studies (the type in which people are asked about their dietary habits and then followed for years or decades). As a whole, other evidence points in the same direction.
  • Half True: This indicates that a claim contains an element of truth because some aspect of it is supported by solid science. For example, the claim may be valid for a limited number of people or in limited circumstances. But overall, it's misleading.
  • Weak Evidence: This means the claim is not believable based on the available evidence. The supporting research may be very limited or nonexistent. If there's a body of research, the bulk of it refutes the claim, or indisputable scientific facts shoot it down.
Let's start by looking at four very common weight-loss claims.

Acai Berries Help You Lose Weight: Weak Evidence
Sasha Conrad is a success story—or so it would seem. On her blog, the working mother of two children tells how acai berries helped her lose 25 pounds, and she's posted photos to prove it. Nadia Johnson achieved similar results, which she also documented with before and after pictures on her blog. More than 60 other women have posted similar stories, along with photos, on their blogs as well. Sounds impressive until you know this: The pictures are all of the same woman. Her photo was purchased from a stock photography library and digitally altered to make her look thin for the "after" pictures. What's more, many of these blogs contain identical wording. It's all a big scam to sell acai berries, which was exposed by a legitimate blog called As for claims that acai berries promote weight loss, they're no more believable than the bogus blogs.

Acai (pronounced ah-sigh-EE) is a berry from Brazil that's been widely touted in the United States for its health-enhancing powers. In addition to removing toxins and increasing energy, the alleged benefits include burning fat, reducing food cravings, and boosting metabolism. Typically the berry is sold in the form of juice (for as much as $40 a bottle), capsules, or powder. What supposedly makes acai berries so beneficial is their high levels of antioxidants, which help fight harmful free radicals. While some studies show that the berries are rich in antioxidants, other research has found that acai juice ranks in the middle of the antioxidant scale, below Concord grape juice but above apple juice. Whatever the case, antioxidant activity doesn't tell us whether the berries have benefits. That requires human studies showing that they actually lead to weight loss or other purported effects, and so far such research is lacking. This hasn't stopped claims on the Internet that acai berries can help you lose 20 pounds in 20 days or that they result in "450 percent more weight loss than dieting and exercising alone." Some sites falsely claim that Oprah Winfrey endorses their products, which has prompted her to file a lawsuit against a number of marketers.

As long as you don't count on it to melt away pounds or perform other health miracles, acai juice is a perfectly fine beverage. Just watch out for brands with added sugar and calories. Also, beware of sites that offer "risk-free" trials for acai products. The Center for Science in the Public Interest reports that many consumers who signed up for such deals have been hit with monthly charges of $80 or more on their credit cards, which continued after they tried to cancel.

To warn others, maybe these folks should post blogs with pictures of their shrinking wallets. If they're interested, I'd be happy to sell them photos.

Dairy Products Promote Weight Loss: Weak Evidence
Sometimes advertising messages stick with us long after the ads are gone: Coca- Cola is the "Real Thing," Timex "Takes a Licking and Keeps on Ticking," Kentucky Fried Chicken is "Finger- Lickin' Good." To that list I would add "Milk Your Diet. Lose Weight!" For years, an array of milk- mustachioed celebrities, ranging from David Beckham to Dr. Phil, urged us to drink milk as a way to slim down. Though the ubiquitous ads were discontinued in 2007, the notion they promoted lives on.

The ads were part of a massive marketing effort by the dairy industry, which also included community events and weight-loss contests with cash prizes. All pushed the message that three daily servings of dairy products could help dieters burn fat and shed extra pounds. This notion didn't come out of nowhere. Some observational studies had found that people who consumed more calcium—whether through supplements or dairy products—tended to be thinner than those who got less. Also, several small, short- term studies showed that subjects put on a high-dairy, reduced-calorie diet lost more weight and fat than low-dairy dieters. All were conducted by a dairy-funded researcher at the University of Tennessee who had patented the dairy weight-loss claim and sold licensing rights to the dairy industry.

After other scientists expressed skepticism and consumer activists cried foul with the Federal Trade Commission, the dairy industry decided to suspend its campaign "until further research provides stronger, more conclusive evidence of an association between dairy consumption and weight loss." Well, there's now further research, including several clinical trials, and overall it shows no greater weight or fat loss among subjects on high-dairy diets. A few studies have even linked dairy to weight gain. The Tennessee researcher who got positive results has said that the problem is with everyone else's study designs. Many did not put subjects on a calorie-restricted diet, which he says is necessary for dairy to have an effect. Another shortcoming he cites is that not all participants had a calcium deficiency, something he says is essential for dairy to work its alleged magic. Oh, and add to the list that you must be overweight and not on a high-protein diet. Such caveats are neither clear nor relevant to most consumers.

What the ads said—and what many people continue to hear and believe— is that milk and other dairy products can help you lose weight. Period. If the ads ever come back, maybe they'll look like those giveaways of cash and cruises with all the fine print:

EAT DAIRY. LOSE WEIGHT!* *Only if you're overweight and on a calorie-restricted diet that's otherwise too low in calcium and not too high in protein. Restrictions apply. Void where prohibited.

Green Tea Promotes Weight Loss: Half True
Over the years, I've seen more questionable products for weight loss than I can count. Things like seaweed patches that allegedly boost your metabolism, rings for your finger that supposedly have the same effect as jogging six miles, and insoles for your shoes that purportedly prompt your body to burn fat. Then there's green tea. The drink's reputation as a weight-loss aid took off after a diet book author claimed on Oprah that by simply switching from coffee to green tea, people could lose body fat "very rapidly" and shed 10 pounds in six weeks. When Coca-Cola and Nestlé tried to jump on the bandwagon with a beverage made of green tea extracts that would supposedly help burn extra calories, they were hit with an investigation by 28 states for making unsubstantiated claims. Eventually, they agreed to pay a fine and change their marketing to say that the drink, called Enviga, couldn't produce weight loss without dieting and exercise.

Given all the hype, green tea would seem to rank up there with diet rings and seaweed patches. In truth, it can really help burn extra calories—though probably not enough to make much of a difference. Green tea contains an antioxidant known as epigallocatechin gallate (EGCG), which has been shown in lab studies to boost metabolism and fat burning. The caffeine in tea is thought to have similar effects. In a study of 10 men, the combination of EGCG and caffeine caused subjects to burn more energy over a 24-hour period than did caffeine alone or a placebo.

A number of small randomized trials have tested whether tea supplements containing these ingredients or can produce weight loss. When researchers pooled data from 13 such studies, they found that subjects taking EGCG plus caffeine, typically for three months, shed one to three pounds more than those getting a placebo. Such a small difference, the authors noted, is "not likely clinically relevant." It's unknown whether you can lose more pounds over a longer period of time or whether the weight stays off. What's more, it's not clear exactly how much green tea you need to consume because studies have used various doses of EGCG and caffeine. The populations studied have varied as well, which means scientists aren't certain who is most likely to benefit. Another unknown is the long- term safety of green tea supplements. In more than two dozen cases, they've been linked to liver damage, especially when taken on an empty stomach.

If you want to give green tea a try, your best bet is to stick with beverages instead of pills. While it may give your metabolism a small boost, don't count on it to put you in shape for swimsuit season. That's especially true if you prefer your tea in the form of Jamba Juice smoothies or Starbucks Frappuccinos, which can come loaded with more than 400 calories. Compared to that, you'd be better off with fat- burning insoles. At least they're calorie free—and they might make your shoes more comfortable.

Carbs Help You Lose Weight: Weak Evidence
When I first heard a reference to "morning banana," I assumed it was the name of some wacky drive- time deejay. Well, I was right about the wacky part. It's actually a weight-loss diet that involves eating only bananas in the morning, followed by whatever you want for lunch or dinner. After a singer in Japan claimed that she'd lost 15 pounds on the regimen, sales of the fruit surged so much in that country that it experienced a banana shortage. Proponents say a key component of this diet is something called resistant starch (RS), so named because it resists being broken down and absorbed as it passes through the small intestine. RS is found in not only bananas (especially green ones) but also foods such as potatoes, bread, and pasta—things that get the ax from Atkins and other low-carb diets. But these are the star attraction in weight-loss plans like the Skinny Carbs Diet and the Carb- Lovers Diet, which claim that RS can help you shed pounds by burning fat and reducing hunger. While preliminary studies seem to provide a bit of support for the idea, I wouldn't go bananas over it.

How foods are processed and cooked affects how much RS they contain. High on the list are unprocessed whole grains, corn flakes, uncooked rolled oats, white beans, cold pasta, raw potatoes, and cooked potatoes that have been cooled. RS also comes in the form of specially formulated cornstarch that can be sprinkled into foods or used as a substitute for flour. Lab studies have found that feeding rodents a high RS diet results in less body fat, perhaps by increasing levels of hormones that make the animals feel full and stop eating. Advocates of RS diets often point to that research along with a human study in which subjects were fed four meals with varying amounts of RS. The meal containing about 5 percent RS (as a fraction of total carbs) resulted in 23 percent more fat burning than the one with no RS.

Sounds impressive until you know a few details: The study consisted of just 12 subjects, they ate just one of each meal, and testing lasted for just 24 hours. In general, human studies—all of them small and short term—have yielded mixed results. Some show that RS increases feelings of fullness or results in lower food intake, but other research has found no such effects. There's little if any direct evidence that eating RS leads to weight loss, even in the short run. If high RS diets do help you shed pounds, it may be because many RS foods are rich in fiber, which has been linked to lower body weight.

In any event, you can't go wrong with oats, beans, brown rice, and other RS foods that are part of a healthful diet. But I'll skip the green morning bananas, thanks.

Adapted with permission from "Coffee is Good for You" by Robert J. Davis, PhD, by arrangement with Perigee, a member of Penguin Group (USA) Inc., Copyright (c) 2012 by Robert J. Davis, PhD, MPH.