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The Paleo Diet: What Does the Science Say?

By Kalyn Weber Feb 19, 2014

 

The Paleo diet is the latest craze in the world of nutrition and fitness. Supporters often describe this diet as a lifestyle, which is centered on eating similar foods and food groups to our hunter-gatherer ancestors and what they survived on during the Paleolithic era. Dieticians and other health professionals have criticized the movement for its denouncement of two key components of the MyPlate guide: grains and dairy. Like other diets, the caveman lifestyle has been described as overly restrictive and difficult to adhere to. paleo_science

What does the scientific literature reveal about the Paleo trend?

Here are some highlights from recent studies on the Paleo diet:

Just last month, a study was published in the European Journal of Clinical Nutrition that suggests that a Paleo-like diet may lead to decreased waist circumferences and blood triglycerides after 6 to 12 months. At least it did in their population of 70 obese postmenopausal women. The problem? These outcomes were not observed at the 2-year follow-up mark, which tends to be the case for most diets. Individuals often do well early on with their diet plans, but then are unable to maintain success later on. A recent study of 10, healthy, postmenopausal women showed positive health outcomes linked to the Paleo diet. The women were instructed to eat a paleo-like diet ad-libitum (Latin for “at one’s pleasure”) for 5 weeks. The results? Women, on average, consumed fewer calories, weighed less and significantly decreased their waist and hip circumference, and diastolic blood pressure. Participants’ blood levels of biomarkers such as fasting serum glucose, cholesterol, and triglycerides all decreased as well.  

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Another crossover study design compared participants’ health outcomes with their typical diet, to the health outcomes after consuming a paleo-type diet for 10 days. While participants did not lose weight, researchers concluded from the study that “even short-term consumption of a Paleolithic-type diet improves blood pressure and glucose tolerance, decreases insulin secretion, increases insulin sensitivity and improves lipid profiles.”  An earlier study examined the relationship between two different diet types – Mediterranean versus Paleolithic – and glucose tolerance. Impaired glucose tolerance, a pre-diabetic state of hyperglycemia that is associated with insulin resistance and increased risk of cardiovascular disease, actually improved to a greater degree in Paleo dieters. Mean waist circumference also decreased to a greater degree for the Paleo individuals. A follow-up study in 2009 found similar results, using a randomized cross-over design. Researchers assigned 13 diabetic participants to follow a Paleo diet, based on lean meat, fish, fruits, vegetables (including root vegetables), eggs and nuts for 3-month study periods. The study yielded similar results and the researchers concluded that the “Paleolithic diet improved glycemic control and several cardiovascular risk factors compared to a diabetes diet in patients with type 2 diabetes.

Conclusions

At first glance, this seems like good news for Paleo subscribers. Paleo critics have long cited that this diet promotes higher intakes of saturated fats – a risk factor for cardiovascular disease. However, these studies indicate that the Paleo diet may actually be protective against cardiovascular disease, at least in terms of risk factors such as glucose and lipid profiles, waist circumference, blood pressure and cholesterol.

Unfortunately, most of the studies cited above have serious limitations — the chief of which is small sample size. These studies are small and mostly non-representative of the average American, much less the average athlete (many use postmenopausal women or a sick population). For example, study 4 from above, albeit with the largest sample size, studied 29 individuals with both ischaemic heart disease AND glucose intolerance or type 2 diabetes (not exactly a starting point of perfect health). Because of this, the extrapolation of these findings, and their relevance to the average American, should be questioned.

The second issue with the majority of these studies is a short time period. The Paleo diet is often described as a “lifestyle change,” but there doesn’t seem to be any longitudinal data on its effects. While weight loss can happen relatively quickly, i.e. a few weeks or months, chronic diseases develop over long periods of time. Therefore, it is probably unwise to make certain types of life-long assumptions based on studies that were conducted over short periods of time.

What does this mean for me?

The evidence is not strong enough yet for health professionals to be changing the dietary recommendations. Does that mean Paleo is wrong for you? Maybe not. Individuals with gluten or dairy intolerances may still find great benefit. And as you have seen, there is fairly consistent evidence of weight loss and cardiovascular improvements stemming from the Paleo diet.

It is important to note, weight loss was not maintained in most of these studies. As with most low-carb, restrictive diets, rapid weight loss often occurs quickly in the first few weeks of the diet. This is because your body is breaking down muscle and fat to use as fuel. To dilute the breakdown of these tissues, you excrete more fluid and shed a large portion of your water weight. The weight you observe is just water weight! After this beginning phase, your weight loss will plateau and you are more likely to gain weight if you do not maintain your diet.

As with any change you make to your fitness plan, it’s important to monitor the effects of these changes. With InsideTracker, you can track important biomarkers of health and metabolism, like fasting glucose, cholesterol, triglycerides, as well as biomarkers for key nutrients, like sodium, potassium and vitamin D, no matter if you follow Paleo, Mediterranean, or any other diet.