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Apr 20

Does the Paleo Diet make you Fat? (Part 1)

The Paleo diet is the latest in a series of eating plans which claim that a low-carbohydrate diet is closer to the way that our primitive ancestors ate than the high-carbohydrate Western diet.  Paleo enthusiasts argue that this ancestral diet is beneficial for human health, and in particular is likely to be helpful in the fight against the chronic diseases that plague Western society, such as heart disease, type II diabetes and metabolic syndrome.

Plump mouse with food

Did a Paleo diet make mice fat?

Study Questions Beliefs

A recently published study has questioned this thinking.  Researchers in Australia fed mice either a standard diet or a low-carbohydrate, high-fat diet for 9 weeks.  After 5 weeks they noticed that the mice on the low-carbohydrate diet had gained significantly more weight than the mice on the standard diet.  Furthermore, the mice on the low-carbohydrate diet had significantly higher levels of insulin in their blood after feeding, and a reduced ability to tolerate sugar when compared to mice on a standard diet.  The researchers concluded that the problems of weight gain, insulin resistance, and the body’s ability to handle sugar were likely to be made worse, not better, on a Paleo-style diet (1).

So should the Paleo diet be thrown out with last year’s newspapers?  Not necessarily.  Taking a closer look at this study reveals that all is not as it seems.

What did the mice eat?

The diet which the mice were fed during the study bears no resemblance to any human diet.  In the low-carbohydrate mouse diet, 81% of the energy came from fat, with only 6% from carbohydrate (the rest of the energy came from protein).  The only source of carbohydrate for the mice was sucrose – that’s table sugar!  Loren Cordain, the original ‘Mr Paleo’, suggests that in a true ancestral diet 22-40% of energy came from carbohydrate (2), and of course none of that came from table sugar.  In a modern low-carbohydrate diet, the carbohydrate content is likely to reflect the ancestral pattern, and is mostly derived from vegetables and certain fruits, none of which the mice in these studies had access to.  The diet would also be likely to include a higher proportion of protein and a lower proportion of fat than these mice were fed.

Stack of vegetables

Modern low-carbohydrate diets have vegetables and fruit as their carbohydrate source, which confer a wealth of other benefits.

In short, the mice in the study were fed a sugar-containing, very high fat, low protein diet.  This is neither a Paleo diet, nor does it reflect any other dietary model which claims health benefits.  Further, it is lacking in three essential components of a healthy diet namely:

  1. Dietary fibre

  2. Vitamins, minerals and plant nutrients

  3. Prebiotics – foods, often plant-based, which encourage a healthy balance of intestinal bacteria.

There is little doubt that all of these groups of nutrients are key elements of a healthy diet, and are helpful for weight management.  There is particular interest at the moment in the role which healthy intestinal flora play in weight and obesity (3).

Adding it Up

It’s also worth noting that the study only involved a total of 17 mice, 8 of which were fed the low-carbohydrate diet.  All the mice were specifically bred to be prone to obesity.  This is a very small study of a very specific group, and the subjects are not even human!

Whilst the diet fed to these mice did indeed make them overweight and contribute to insulin resistance it is not a diet that anyone would contemplate feeding to a person.  The mouse diet was not a Paleo diet, so it cannot answer the question of whether Paleo or other low-carbohydrate diets are good or bad for human health.

Fortunately there are other studies which contribute to our understanding of this question.  Join me again soon to find out whether or not there is any evidence that Paleo-style diets make you fat.

References:

  1. Lamont, B.J., Waters, M.F., & Andrikopolous, S., (2016). A low-carbohydrate high-fat diet increases weight gain and does not improve glucose tolerance, insulin secretion or β-cell mass in NZO mice.  Nutrition and Diabetes, 6, e194, Published online February 2016.
  2. https://paleodiabetic.com/2011/09/19/is-the-paleo-diet-low-carb/ [Accessed 20 April 2016].
  3. Barczynska, R., Bandurska, K., Slizewska, K., Litwin, M., Szalecki, M., Libudzizi, Z., & Kupusniak, J., (2015).  Intestinal Microbiota, Obesity and Prebiotics  Polish Journal of Microbiology, 64(2), 93-100.

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