A more recent fad, the Paleo diet plan claims to emulate the “natural” diet of humans who lived in the Paleolithic period, also commonly called the “Stone Age.”

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You’ve no doubt heard about diets that claim to quickly and easily boost your heart health, melt off extra pounds, and even improve your memory. Most fad diet plans have some nuggets of good advice, but many of these diets go to extremes, and some may have potentially dangerous side effects. Do these diets have anything to offer for a healthy heart and brain?

1. Low-Carb “Revolution”

Consider the “low-carb” craze. Americans hardly thought about “carbs” at all until the Atkins “diet revolution.” Proponents of low-carbohydrate diets claim that eating fewer carbohydrates forces your body to burn stored fat for energy. When you digest carbohydrates, your body converts them to sugar. As your blood sugar level rises, your body produces more insulin, which transports the sugar from your blood into your cells for energy. When you restrict carbohydrates, you produce less insulin, forcing your body to use stored fat for energy instead.

Unfortunately, going “low-carb” means restricting healthy whole grains, fruits, vegetables, legumes, milk, and yogurt, which all contain carbohydrates. In addition, Tufts researchers led by Holly Taylor, PhD, have found some evidence that eating too few carbohydrates might deny your brain the nutrients it needs to think clearly. If you’re not getting enough carbs in your diet, you may experience decreased cognitive performance.

However, it is true that research suggests foods high in refined carbohydrates, such as white flour and added sugar, contribute to weight gain and diabetes risk. Since both of these conditions are unhealthy for your heart and brain, it’s wise to watch out for these types of carbs.

2. Low-Fat Failure

It makes sense that following a low-fat diet means consuming fewer calories overall because fats are a concentrated form of calories—nine calories per gram, compared to four calories per gram of protein or carbohydrate. In the 1980s, low-fat foods became very popular, and food manufacturers produced fat-free and reduced-fat versions of cookies (epitomized by Snackwells), brownies, crackers, chips, and many other processed foods. Eating these “diet” versions of junk food did little to improve people’s diets and instead contributed to the obesity epidemic. As noted earlier, the latest dietary guidelines do not recommend a low-fat dietary pattern; instead, they advise getting most of your fat from plant foods that provide unsaturated fat and minimizing your consumption of saturated and trans fats.

Studies have found that low-carb and low-fat diet plans work equally well for weight loss, at least in the short term. Experts advise that any diet you find easy to stick to—which is typically true of those with a simple “eat less of this” mantra—can be effective. Neither low-carb nor low-fat eating is a nutritious prescription for lifelong health, however.

While it’s true that any diet plan that is too permissive won’t help you control your weight or protect your heart and brain, it’s also true that any diet that forces you to deny yourself all of the foods you love is likely to be short-lived.

3. Paleo Promises

A more recent fad, the Paleo diet plan claims to emulate the “natural” diet of humans who lived in the Paleolithic period, also commonly called the “Stone Age.” Anthropologists have pointed out, however, that the actual diets of early humans were varied and opportunistic—in other words, they ate what they could find. If early humans were less prone to such “diseases of affluence” as heart disease, it’s likely because they died too young to develop such conditions.

The Paleo diet recommends eating grass-fed meats, fish and seafood, fresh fruits and vegetables, eggs, nuts and seeds, and oils from nuts, seeds, olives, avocados, and coconuts. Paleo devotees avoid cereal grains, legumes, dairy products, potatoes, refined vegetable oils, processed foods, sugar and other commercial sweeteners, and salt.

In practice, the Paleo diet often becomes an excuse to eat a lot of meat. While meat is high in protein, most Americans already get plenty of protein in their diets. Many cuts of meat are high in saturated fat, the leading dietary cause of unhealthy cholesterol levels. Whether the grass-fed beef recommended in the Paleo diet is really healthier remains a subject of debate. One review found that grass-fed beef is lower in saturated fat and higher in healthy fats, including omega-3s, and other beneficial nutrients.

Goodbye to Grains

While the Paleo diet plan cuts out some unhealthy ingredients, such as salt and sugar, it also omits foods recommended by nutrition experts, such as whole grains, legumes, and dairy. “It demonizes whole grains,” says Zach S. Conrad, PhD, a former Tufts postdoctoral fellow who is now a research nutritionist at the USDA’s Grand Forks Human Nutrition Research Center. “It’s possible to consume a well-rounded diet without whole grains, but it’s difficult. By also cutting out legumes, the diet loses most complex carbohydrates.”

As for sugars, there’s little evidence that choosing “natural” sweeteners, such as agave nectar, date sugar, honey, or maple syrup, rather than granulated sugar or other commercially produced sweeteners, has health benefits. All of these sweeteners contain roughly the same amount of calories and affect the body similarly.

Fruits and vegetables endorsed by Paleo promoters are good sources of nutrition, but most were not actually available to our Paleolithic forebears. Broccoli, for example, was not cultivated in its present form until about 2,000 years ago.

No Calorie Limits

Most so-called Paleo diets don’t set any limits for calories, since our Paleolithic ancestors often struggled to get enough. In our calorie-rich modern world, however, failing to limit calories in any dietary regimen can lead to weight gain and obesity.

The Paleo diet plan is not endorsed by the American Diabetes Association, the American Heart Association, or any other large, reputable health organizations. A few small, short-term studies have some benefits from the diet, but there is not enough evidence to recommend it.

For more information about diet plans for heart and brain health, purchase The Heart-Brain Diet at www.UniversityHealthNews.com.