Science and Low Carb / Paleo
This page summarizes some of the science behind low carb / paleo diets.
Saturated fat
Despite half a century of research there is still no evidence that natural saturated fat (like butter, eggs etc.) is anything but completely safe to eat.
Have a look at these recent reviews of all the evidence:
”Insufficient evidence of association is present for intake of … saturated or polyunsaturated fatty acids; total fat … meat, eggs and milk.”
- Mente A, et al. A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Arch Intern Med. 2009 Apr 13;169(7):659-69.
”There were no clear effects of dietary fat changes on total mortality or cardiovascular mortality”
- Hooper L, et al. Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev. 2011 Jul 6;(7):CD002137.
”…no significant evidence for
concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.”
- Siri-Tarino PW, et al. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010 Mar;91(3):535-46.
This means that the scientific foundation of todays low fat dietary advice has fallen. The reasons today are mainly political and economical, combined with old-fashioned prestige and inertia.
The low fat dietary advice has become a house of cards with nothing to support it. It is just a question of time before this is apparent to everybody.
Weight loss
Some people still claim that weight loss studies do not show any advantage for low carb diets. Unbelievably enough, that is what many so called experts still believe.
It’s either ignorance or science denial.
There are at least fourteen modern scientific studies of the highest quality (RCT) that show significantly better weight loss with low carb diets. See for yourself:
RCTs showing significantly more weight loss with low carb diets
- Brehm BJ, et al. A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet on Body Weight and Cardiovascular Risk Factors in Healthy Women. J Clin Endocrinol Metab 2003;88:1617–1623.
- Samaha FF, et al. A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity. N Engl J Med 2003;348:2074–81.
- Sondike SB, et al. Effects of a low-carbohydrate diet on weight loss and cardiovascular risk factor in overweight adolescents. J Pediatr. 2003 Mar;142(3):253–8.
- Aude YW, et al. The National Cholesterol Education Program Diet vs a Diet Lower in Carbohydrates and Higher in Protein and Monounsaturated Fat. A Randomized Trial. Arch Intern Med. 2004;164:2141–2146.
- Volek JS, et al. Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women. Nutrition & Metabolism 2004, 1:13.
- Yancy WS Jr, et al. A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia. A Randomized, Controlled Trial. Ann Intern Med. 2004;140:769–777.
- Nichols-Richardsson SM, et al. Perceived Hunger Is Lower and Weight Loss Is Greater in Overweight Premenopausal Women Consuming a Low-Carbohydrate/High- Protein vs High-Carbohydrate/Low-Fat Diet. J Am Diet Assoc. 2005;105:1433–1437.
- Gardner CD, et al. Comparison of the Atkins, Zone, Ornish, and learn Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women. The a to z Weight Loss Study: A Randomized Trial. JAMA. 2007;297:969–977.
- Dyson PA, et al. A low-carbohydrate diet is more effective in reducing body weight than healthy eating in both diabetic and non-diabetic subjects. Diabet Med. 2007 Dec;24(12):1430-5.
- Shai I, et al. Weight loss with a low-carbohydrate, mediterranean, or low-fat diet. N Engl J Med 2008;359(3);229–41.
- Krebs NF, et al. Efficacy and Safety of a High Protein, Low Carbohydrate Diet for Weight Loss in Severely Obese Adolescents. J Pediatr 2010;157:252-8.
- Summer SS, et al. Adiponectin Changes in Relation to the Macronutrient Composition of a Weight-Loss Diet. Obesity (Silver Spring). 2011 Mar 31. [Epub ahead of print]
- Daly ME, et al. Short-term effects of severe dietary carbohydrate-restriction advice in Type 2 diabetes–a randomized controlled trial. Diabet Med. 2006 Jan;23(1):15–20.
- Westman EC, et al. The effect of a low-carbohydrate, ketogenic diet versus a low- glycemic index diet on glycemic control in type 2 diabetes mellitus. Nutr. Metab (Lond.)2008 Dec 19;5:36.
14-0
The first twelve studies in the list are weight loss trials, the last two are studies on type 2-diabetics (usually overweight) showing the same effect. Many of the studies are of six months or one year duration, one of them (Shai et al) is two years long.
All of these studies show significantly more weight loss for the group that were adviced to eat a low carb diet (Atkins, in most cases).
As far as I know the opposite has never been shown: low carb has never lost a weight loss trial significantly. This means that low carb is winning versus the failed low fat/low calorie advice by 14-0!
Feel free to let me know of any exceptions (or more examples) in the comments.
Update an expert
It’s not OK for “experts” to keep denying all these modern trials. It’s time for them to take the science seriously.
Feel free to copy or link to this list, if you encounter an expert who needs an update.
More
September 25, 2011 at 22:45
Dietary Carbohydrate Modifies the Inverse Association Between Saturated Fat Intake and Cholesterol on Very Low-Density Lipoproteins
Free full text at link
We aimed to investigate the relationship between dietary saturated fat on fasting triglyceride (TG) and cholesterol levels, and any mediation of this relationship by dietary carbohydrate intake.
Men and women in the NHLBI Genetics of Lipid-Lowering Drugs and Diet Network (GOLDN) study (n = 1036, mean age ± SD = 49 ± 16 y) were included.
Mixed linear models were run with saturated fat as a predictor variable and fasting TG, very low density lipoprotein cholesterol (VLDL-C), low density cholesterol (LDL-C) and high density cholesterol (HDL-C) as separate outcome variables.
Subsequent models were run which included dietary carbohydrate as a predictor variable, and an interaction term between saturated fat and carbohydrate.
All models controlled for age, sex, BMI, blood pressure and dietary covariates.
In models that included only saturated fat as a predictor, saturated fat did not show significant associations with fasting lipids.
When carbohydrate intake and an interaction term between carbohydrates and saturated fat intake was included, carbohydrate intake did not associate with lipids, but there was an inverse relationship between saturated fat intake and VLDL-C (P = 0.01) with a significant interaction (P = 0.01) between saturated fat and carbohydrate with regard to fasting VLDL-C concentrations.
Similar results were observed for fasting TG levels.
We conclude that, when controlling for carbohydrate intake, higher saturated fat was associated with lower VLDL-C and TGs.
This was not the case at higher intakes of carbohydrate.
This has important implications for dietary advice aimed at reducing TG and VLDL-C levels.
So when is Saturated fat harmful?
When it is associated with higher carbohydrate intakes.
October 3, 2011 at 8:36
Thanks for this great collection of articles outlining the importance of eating saturated fats and dismissing the false science that has fueled a huge industry of low-fat foods that has caused such harm to our health. I sure hope more people in the US learn about this and change their diets.
October 4, 2011 at 4:41
Are there similar studies showing the adoption of a LCHF diet decreases LDL cholesterol, total cholesterol or even outcomes like coronary artery disease?
October 4, 2011 at 22:27
@3
No, not that much, thats a over simplicity explanation, and its goes in the other direction to.
The old thougts was that fat course high cholesterol and that was the reason to heart diseses, its not.
High colesterol is more complicated then that, but some whith syndrom X and similar condition often get better blod lipids, becuse high insulin levels provoke the liver to produce a lot of triglycerids an smll LDL.
One thing you can say is that more fat and less carbs often result in better HDL/LDL ratio and lower VLDL.
Its this fat/cholesterol hypotes thats totaly wrong!