Sunday, October 13, 2013

Other Paleolithic Diet Trials: Part 2

See Part 1 for the uncontrolled trials before 2010

A Palaeolithic-type diet causes strong tissue-specific effects on ectopic fat deposition in obese postmenopausal women (2013) 

10 healthy, post-menopausal women, with a BMI of (28-35) ate a Paleo diet for 5 weeks.  Participants were given prepared meal portions for breakfast, lunch and dinner that were roughly 30:40:30 (protein:fat:carbs).  The Paleo diet included "lean meat, fish, fruit, vegetables (including root vegetables), eggs and nuts", and excluded  "dairy products, cereals, beans, refined fats and sugar, added salt, bakery products and soft drinks were excluded".  The diet was ad libitum so they could have extra of the allowed foods.  Calories burned through exercise didn't change

Energy (kcal)
Protein (%)
Fat (%)
Carbohydrate (%)
Sucrose (%)

They lost weight (86.4 to 81.8) and reduced their blood pressure, heart rate, fasting glucose and insulin, HDL-C and LDL-C (by a similar proportion), HDL-P and LDL-P (by a similar proportion) and triglycerides (see table 1 and 3).  And as the title suggests, average liver fat decreased, which is probably responsible for the improvements in liver insulin sensitivity, although whole body insulin sensitivity and muscle fat stores (not necessarily bad) didn't improve

However, the increased protein and can partially explain the weight loss and the protein and weight loss can explain the reduction in liver fat.  Without a control group which lost a similar degree of weight, or unless the Paleo group was kept weight stable, you can't conclude that the Paleo diet had a special effect on liver fat.  It's odd that HDL-C and HDL-P decreased seeing as replacing carbs with fat, weight loss and lower triglycerides are three factors that would increase HDL-C (and perhaps HDL-P?)

(You may remember that this study came out earlier this year in May.  As expected, many in the anti-Paleo crowd linked it and the some in the Paleo community raised some really quite irrelevant objections.) 

43 Healthy participants (23 male, 20 female), in their early 30’s were asked to eat an ad libitum Paleo diet for 10 weeks and participate in a CrossFit-based, high-intensity circuit training exercise program 

Paleolithic Diet
“A Paleolithic diet, as first described by Eaton and Konner, was implemented for all study participants. Subjects were advised to increase their consumption of lean meat, fish, eggs, nuts, fruit, and vegetables and were instructed to strictly avoid all grains, dairy products, and legumes. All modern, processed foods including any form of processed sugar, soft drinks, and coffees were also excluded from the diets of the subjects. No specific macronutrient recommendations were made, as the study design wanted to closely mimic a real world model that would incorporate food choices made by the average consumer. Intake of specific proportion of food categories (e.g. animal vs. plant foods) was also not given.” 

We aren’t given much information on what the participants actually ate except for: “Analysis of 3-day diet recalls revealed that subjects were eating an average of 49.75% of daily caloric intake from fat, 13.1% of daily caloric intake from saturated fat, 672.7 mg of dietary cholesterol, and only 25 g of fiber per day.”  Which only came from 8 returned diet logs 

After 10 Weeks
Total Cholesterol (mg/dl)*
n-HDL (mg/dl)*
LDL (mg/dl)*
HDL (mg/dl)
Triglycerides (mg/dl)
Body Fat (%)*
Body Weight (lb)*
Relative VO2 Max (ml/kg/min)*
Oxygen Consumption (ml/min)*
* Significant 

Most of these results aren’t terribly surprising.  You would expect body fat % and weight to decrease with almost any diet + exercise plan, and expect relative VO2 max and oxygen consumption to increase from an exercise plan like Crossfit. 

As for the blood lipids: It’s impossible to know for sure what the participants ate previously and for that matter what they ate during the trial.  I’m just going to generalise from the 8 diet logs and assume on average they increased fat, SFA and lowered carbohydrates.  Although since SFA made up only a small portion of total fat they probably increased MUFA and/or PUFA as well.  From the macronutrients alone you would expect: 

  • Increased HDL-C and lower triglycerides, because replacing carbs with either SFA, MUFA or PUFA raises HDL-C and lowers triglycerides [1]
  • A lower total cholesterol to HDL-C ratio, because replacing carbs with any whole food fats reduces the ratio [1] 

You wouldn’t know what to expect with LDL-C and total cholesterol (TC) because SFA raises TC and LDL-C, MUFA decreases LDL-C by a small amount, but not TC and PUFA lowers TC and LDL-C.  In the table below I guessed what they previously ate and the MUFA and PUFA in their Paleo diet.  I could be horribly wrong, but the point is these guestimates suggest most of the increase in fat would have come from MUFAs and PUFAs, which would be expected to reduce TC and LDL-C (unless they tanked their thyroid doing low carb + Crossfit) 

Previous Diet
Paleo Diet
Fat (%)
33.5 [2] (US average)
SFA (%)
11 [2] (US average)
MUFA (%)
PUFA (%)

In the discussion, the author suggests active weight loss may explain why the HDL-C was lower than expected and why the triglycerides were higher than expected. 

But what about the LDL-C?  Perhaps the participants underreported eating SFA rich foods or they were previously eating oats, margarine and a lower SFA, higher PUFA duet (than the US average) to lower their cholesterol 

What I liked about the study is that it looked at the effect of a Paleo diet in healthy participants.  But at the end of the day where’s the pathology?  The tiny increase in LDL-C is not a big deal and the other lipids may have been confounded by active weight loss. 

* If one were only looking at the effect of macros, the results suggest that the participants replaced MUFA and PUFA with carbs

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