The Paleo Perspective: Is Fossil 'Fuel' the Solution to Our Obesity Epidemic?

The diet industry in the United States is comparable to the fashion industry: Both thrive on short-lived trends that are always evolving. This can create a large extent of confusion for consumers swayed by the trends. The best types of diets (think Mediterranean diet and the DASH diet) are similar to a timeless pair of diamond earrings, which remain relevant from year to year.

The paleo diet trend has resurfaced in recent years as a method for weight loss and healthy living. Before jumping onboard, it's important to evaluate whether or not the diet is effective and, most importantly, sustainable. This back-to-the-basics dietary approach incorporates foods that were available 10,000 years ago to our Paleolithic ancestors and eliminates all others. The theory is based on the idea that we should only eat foods that our bodies are genetically predisposed to consume, including lean meat, fish, eggs, vegetables, fruits and nuts. Foods that are excluded from the paleo diet include all cereal grains (both whole and refined), beans and legumes, dairy, refined sugar, caffeine, and alcohol.

The consensus on whether or not this strict diet delivers true health benefits is still up for debate. While the type of diet that you choose to follow is a personal choice, in order to make the best decision on any diet, it's important to be fully aware of the the pros and cons. Adhering to the paleo diet requires discipline, time and commitment -- it's up to you to determine whether the health advantages are worth the extra time and effort. Here are the major pros and cons of the caveman diet:

Cons of the Caveman Diet:

1. The diet is based largely on testimonials.

When purchasing a car, people determine the safety of a vehicle by looking at the tested safety ratings, rather than hearing from a salesman that it's the safest car on the market. The same should be true for diet. Much of the case built for the paleo diet is based on personal testimonials because limited research exists to substantiate any health claims.

An expert panel selected by U.S. News conducted a large, comprehensive review of 32 different diets. Each diet was rated on effectiveness for weight loss, preventing diabetes and heart disease, and feasibility. Of the 32 diets, the paleo diet tied with the Dukan Diet for last place. Experts compared the diet to the Atkins or Eco-Atkins diets and concluded that there is little evidence to show that a Paleolithic diet is effective for weight loss, heart disease or diabetes. The paleo studies that have been conducted are small and short-term when compared to studies on vegetarian diets that frequently include more than 70,000 participants and have proven to be effective after long-term adherence. Before doing away with multiple food groups, I always advise my patients to be sure there are some well-defined health benefits.

[Read: Food for Thought: Can the Paleo Diet Heal Mental Disorders?]

2. There's no clear evidence that the paleo diet leads to weight loss.

There have been approximately five studies conducted to evaluate the effectiveness of weight loss associated with the paleo diet, meaning that, when compared to other popular diets, we should probably wait for more evidence to make a final judgment. One study that was recently published may be one of the most promising. The study includes a larger population (70 overweight, post-menopausal women) and longer duration (two years), compared to past paleo research. The researchers randomly assigned a high fiber, low-fat diet (also known as the Nordic diet) or the Paleolithic diet. After follow-up at six months and again at two years, the paleo group respectively lost approximately four kilograms and 1.5 kilograms more than Nordic participants. Researchers also reported that those on the paleo diet lost more from the mid-section. These results indicate that the paleo diet may be promising, but not much is known about what occurs after two years.

Another new study evaluated whether paleo dietary patterns actually lead to appetite suppression by looking at the colon's microbiota and appetite-suppressing gut hormones. The researchers used fecal bacteria samples of three human vegetarians and three gelada baboons, who eat mainly grass. Some were fed a predigested high-starch, potato diet, while others were fed a predigested high-fiber grass diet. They found that the potato-based diet produced the highest level of appetite-suppressing hormones, which go against the ancestral diet theory. These fascinating results indicate that more research looking at the role of diet and gut bacteria needs to be conducted before making claims that the diet suppresses appetite.

[Read: Easy Recipes for a Paleo Diet.]

3. Meaty (and risky?) on the heart.

Paleo followers advocate for a diet rich in meat, because that's what our ancestors hunted and gathered 10,000 years ago. While this may be true, the meat that was hunted 10,000 years ago has a much different nutrient content than meat sold today. While the paleo diet responsibly recommends grass-fed meat, we should always keep in mind that there may be too much of a good thing with a meat habit.

In fact, according to the available data, meat should not be a regular staple in today's diet. The data indicate that meat eaters are at a greater risk of a high body mass index, cardiovascular disease and Type 2 diabetes. One study that included more than 11,000 participants compared blood pressure levels of meat eaters to fish eaters, vegetarians and vegans, and found that meat eaters had the highest prevalence of hypertension, while vegans had the lowest. An earlier analysis found that vegetarians had a significant 24 percent lower death rate from ischemic heart disease and a non-significant 7 percent lower death rate from cerebrovascular disease compared with non-vegetarians.

Another study found that substituting alternative protein sources (poultry, fish, legumes and nuts) for red meat was associated with significantly lower inflammatory and glucose metabolic biomarkers (CRP, ferritin, hbA1c and fasting insulin).

Studies show that there is a strong association between consumption of red meat and coronary heart disease, likely because of the high saturated fat content. High dietary intake of saturated fat can lead to an increased risk of cardiovascular disease and diabetes. Accordingly, replacing saturated fats with healthy, unsaturated fats found in olive oil, avocado, and walnuts can lower heart disease risk. Most important to remember perhaps is the fact that it is unlikely that our ancestors had the opportunity to eat meat multiple times in a day because food was much harder to come by.

[Read: How Often Should You Eat Red Meat? ]

4. Missing out on the benefits of whole grains.

Human ancestral diet followers are quick to criticize grains for being a major contributor to the obesity epidemic. While there is a small amount of truth to this claim, it does not depict the entire story. Americans do in fact consume too many grains; however, the majority of those calories come from refined grains. In 2010, grains that were mostly refined (in addition to added fats and oil) contributed 405 of the 459 additional calories consumed by Americans, compared to 1970. The real problem is that refined grains, which are high in calories and added sugar but low in nutrients, are replacing the consumption of whole grains, fruits and vegetables.

Whole grains can be a part of a healthy diet today, and teeth of our fossilized ancestors indicate they may have been 10,000 years ago, too. A meta-analysis from 2012 found that compared to those who never or rarely ate whole grains, those that consumed three to five servings of whole grains per day had a 26 percent lower risk of Type 2 diabetes, a 21 percent lower risk of cardiovascular disease and consistently less weight gain. The benefit of eating whole grains (which includes the bran, aleurone layer, germ and endosperm) is that they provide a variety of important nutrients such as cellulose, lignin, beta-glucan, B vitamins, vitamin E, protein, iron and other minerals.

[Watch: Robert Morton: Why the Paleo Lifestyle Works for Me.]

Pros of the Caveman Diet:

1. Rich in fruits and vegetables.

Regardless of the diet you follow, filling up on plenty of fruits and vegetables will deliver a variety of important nutrients, such as potassium, vitamin C, folate, fiber and antioxidants. If there's anything health experts consistently agree on, it's incorporating plenty of produce in the diet to reduce your risk of chronic disease. A study from March 2014 found that eating seven or more servings of fruits and vegetables a day is associated with a 42 percent lower risk of death at any point, compared to those eating just one serving a day. Whether you follow the paleo diet or not, load up on the fruits and veggies!

[Read: 9 Foods Packed With Potassium .]

2. Limited in added sugar.

Americans consume too much sugar, which translates to a decreased intake of essential micronutrients, excessive calorie intake and an increase in body weight. Excessive sugar in the diet increases overall risk for weight gain, heart disease and the major chronic diseases in the United States. A 2013 study suggests that sugar can affect the pumping mechanism of your heart, increasing risk for heart failure. Another study found that the consumption of sugar-sweetened beverages is associated with early deaths related to diabetes, heart disease and cancer. A diet high in added sugar undoubtedly increases risk of weight gain and preventable chronic diseases and should be avoided.

[Read: How and Why to Rid Sugar From Your Diet .]

3. An attention to whole foods means less added sodium.

According to data from the Center for Disease Control and Prevention, the average consumption of sodium in the United States is equivalent to 3,300 milligrams per day. A high sodium intake is directly associated with an increased risk of heart disease. In order to reduce risk of heart disease, it's necessary to cut back on sodium and ramp up consumption of potassium. Potassium is an essential nutrient that is necessary for lowering blood pressure and a short-fall nutrient in the American diet. One study found that Americans eating a diet high in sodium and low in potassium are at a 50 percent increased risk of death from any cause and approximately twice the risk of death from heart disease. Public health data show that reducing average sodium intake to less than 2,300 milligrams per day may be an effective approach to decrease the prevalence of high blood pressure by a projection of 11 million annually.

Overall, the best type of diet to adopt is one that is sustainable long-term. While there are benefits associated with certain aspects of the paleo diet, whether people can maintain it long-term is still to be determined.

[Read: How to Follow the Paleo Diet on a Budget .]

Brigid Titgemeier, M.S., nutrition assistant at the Cleveland Clinic Wellness Institute, contributed to this article.

Kristin Kirkpatrick, MS, RD, LD, is the manager of Wellness Nutrition Services at the Cleveland Clinic Wellness Institute. She is an experienced presenter, an award-winning dietitian, an author and a regular television guest on both local and national shows, as well a contributor to several national magazines and newspapers. The Huffington Post recently named Kristin "one of 25 diet and nutrition experts you need to follow on Twitter." Kirkpatrick's career began in Washington, D.C., lobbying for Medical Nutrition Therapy reform, and from there she went on to become the Regional Coordinator of the National Heart, Lung and Blood Institute's Hearts N Parks program in Maryland. Follow her on Twitter at @KristinKirkpat.