This study is making the rounds of the paleosphere, so I thought I’d take a moment to look into it and see if it lives up to it’s claims that a paleo-’type’ diet ‘has strong and tissue-specific effects on ectopic lipid deposition in postmenopausal women’ (‘ectopic lipid deposition’ = fat deposits on organs and skeletal muscles).
I got my hands on the full text and had a look. Quick synopsis: researchers put 10 overweight and obese, sedentary, post-menopausal women on a diet that they call ‘paleolithic type’ and measured changes to several metabolic and anthropometric measures. The main areas they were looking for changes were fat deposits in the liver and skeletal muscles, and insulin sensitivity, but they measured several other things as well, including:
-waist circumference and waist-hip ratio
“All meals were prepared by the food service at Umeå University Hospital and were weighed and frozen after preparation. The diet included lean meat, fish, fruit, vegetables (including root vegetables), eggs and nuts. Dairy products, cereals, beans, legumes, refined fats and sugar, added salt, bakery products and soft drinks were excluded. Participants were instructed to complement the provided food with other included food items from the list, ad libitum. To enable preparation of additional complete meals at home, the women received 14-day menus together with recipes and instructions regarding portion sizes. They were also advised to
use only rapeseed (canola) or olive oil in food preparation.”
The diet worked out to roughly 30% protein, 40% fat (predominantly PUFA as saturated fat was limited in this study by design, and most of the fat the subjects consumed came from nuts, fish and canola and olive oils. Wait, canola oil? DO YOU EVEN PALEO?). They ate to appetite and documented their intake.
The results were quite good. The subjects lost an average of 10 pounds, blood pressure improved, both waist circumference and waist-hip ratio decreased, and heart rate decreased! And there was indeed a reduction in liver fat! Good stuff! Lets look a little deeper at that. From the study:
“The dietary regimen resulted in a significantly reduced energy intake (520 kcal/day reduction) despite the ad libitum approach. This may be one of the factors contributing to the striking decrease in liver fat content. A series of studies have indeed shown that hypocaloric diets reduce the amount of liver fat.”
Layman’s terms: the subjects spontaneously ate about 500 calories less per day than they had been eating before the study (I talk about why diets high in protein and fiber, like the one in this study, can lead to a spontaneous reduction in caloric intake here. Protein and fiber are satiating and highly thermic foods. Diets rich in protein and fiber, paleo or otherwise, are very good at producing a spontaneous caloric deficit. It’s not magic, it’s science). It’s been established that hypocaloric diets (hypocaloric = fewer calories consumed than burned) reduce liver fat. Rut roh. Are they saying it might have been the calorie reduction that decreased liver fat, not the magic of paleo? Why yes, yes I think they are.
Speaking of which, you know what else a caloric reduction decreases? Weight. Could it be that the subjects lost weight because they were eating fewer calories? That’s certainly where my money is. The study authors note that the weight loss seems out of proportion to the degree of calorie reduction but then go on to acknowledge:
“Possible explanations include over-reporting of energy intake, increased thermogenic effects of protein (versus other macronutrients) and loss of glycogen which may contribute to loss of body water during the study period. Of note, increased
urinary volumes were commonly reported among participants during this intervention.”
Layman’s terms: maybe the subjects were overreporting their food intake. Maybe there’s something to the Thermic Effect of Food dealio (if you didn’t read my post that I linked above on food thermogenesis, you can do it now). Or maybe, just maybe, the low-carb diet they were on did what low-carb diets always do: flushed out several pounds of water weight as the body’s glycogen stores depleted. The subjects did report peeing more, after all.
So, we looked at the anthropometric changes the diet produced, lets take a look at the metabolic changes. Some good news. Blood glucose and insulin both decreased, and total cholesterol, LDL and triglycerides decreased. HDL also decreased though (that’s the good cholesterol), and cortisol increased (cortisol is a stress hormone). So the metabolic measures were a mixed bag, but overall more good than bad. Not so fast though, glucose, insulin and cholesterol all respond favorably to weight loss, as does blood pressure. Could these improved markers be a response to the subjects’ weight loss, which was a response to reduced calorie intake? That conclusion is certainly supported by decades of credible science.
Back to the original aim of the study: to determine if a paleo diet reduces liver fat and increases insulin sensitivity. Liver fat did decrease, but it turns out that whole-body insulin sensitivity didn’t change, nor fat deposition in skeletal muscles:
“…lipid content in skeletal muscles, as determined by 1H-MRS, was unaltered, as was peripheral insulin sensitivity…”
“…exercise regimens must be included to demonstrate effects on muscle/whole-body insulin sensitivity…”
Layman’s terms: to improve insulin sensitivity you gotta move yo’ ass.
Bottom line: paleo is, as fad diets go, pretty decent. It encourages eating nutritious, whole foods, and accentuates protein and vegetables (staples of weight loss diets from the beginning of time). But it’s not magic. The positive outcomes experienced in this study fall right in line with decades of credible science showing similar outcomes from weight loss due to reduced caloric intake. I’m not hating on paleo: paleo is a healthy diet. But promoting the myth that eating paleo will magically reduce weight and improve metabolic markers is irresponsible for one very big reason: it won’t work for everyone, because not everyone will spontaneously eat fewer calories on a paleo diet. Some people will even eat MORE calories on paleo. And when those people don’t magically lose weight and get healthier, they may blame paleo. Or they may blame themselves. They may think they’re just not ‘paleo-ing’ hard enough. Let be honest: paleo is a healthy diet, and some people may lose weight and see health improvements on it because they spontaneously eat less. But it’s the eating less that is responsible for the weight loss, and if you’re NOT one of the people that spontaneously eats less on paleo, it’s not because paleo is bad, or because you’re doing it wrong, or because you’re destined to be fat or whatever else people have come up with to rationalize away undesired results. Paleo is a pretty decent way of eating but it’s not magic, it can’t rewrite the laws of physics.
Improving the quality of your diet is GREAT, and paleo can help some people do that. There are other ways of improving the quality of your diet, though, and there are other ways of optimizing your calorie intake. Lets sweep away the dogma and magical thinking and be realistic. This study shows what countless other studies have shown before it: that calories matter, that food quality ALSO matters, and that exercise is essential for healthy metabolic function. If paleo provides a framework that helps you succeed in those aras, that is fantastic! But it’s one possible helpful tool out of many, and what works for some doesn’t work for others, we must look critically at the causative factors here (calories, weight loss, exercise) if we want to create a balanced and effective path forward and help more people achieve better health.