The Evidence  (source dietdoctor.com)

There are at least 31 modern scientific studies of the highest quality (RCT) that show significantly better weight loss with low carb diets. This according to the latest count by the Public Health Collaboration UK. The number of studies showing the opposite? Zero.

RCTs showing significantly more weight loss with low carb diets

  1. Shai I, et al. Weight loss with a low-carbohydrate, mediterranean, or low-fat diet. N Engl J Med 2008;359(3);229–41.

  2. Bazzano L, et al. Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial. Ann Intern Med. 2014;161(5):309-318.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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]

  13. Halyburton AK, et al. Low- and high-carbohydrate weight-loss diets have similar effects on mood but not cognitive performance. Am J Clin Nutr 2007;86:580–7.

  14. 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.

  15. Keogh JB, et al. Effects of weight loss from a very-low-carbohydrate diet on endothelial function and markers of cardiovascular disease risk in subjects with abdominal obesity. Am J Clin Nutr 2008;87:567–76.

  16. Volek JS, et al. Carbohydrate Restriction has a More Favorable Impact on the Metabolic Syndrome than a Low Fat Diet. Lipids 2009;44:297–309.

  17. Partsalaki I, et al. Metabolic impact of a ketogenic diet compared to a hypocaloric diet in obese children and adolescents. J Pediatr Endocrinol Metab. 2012;25(7-8):697-704.

  18. 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.

  19. 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.

The first 17 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 advised 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 19-0!

Addition – yet another study with similar results, this time on overweight people with type 2 diabetes:

Saslow S, et al. Twelve-month outcomes of a randomized trial of a moderate-carbohydrate versus very low-carbohydrate diet in overweight adults with type 2 diabetes mellitus or prediabetes. Nutrition & Diabetes 7, Article number: 304 (2017).

Meta-analyses

Several meta-analyses of relevant trials have come to the same conclusion as the individual trials above.

Low carb does not just result in more weight loss than other comparison diets, it also results in more fat loss:

Hashimoto Y, et al. Impact of low-carbohydrate diet on body composition: meta-analysis of randomized controlled studies. Obes Rev. 2016 Apr 5. doi: 10.1111/obr.12405. [Epub ahead of print]

Here’s another new meta-analysis showing more weight loss on low carb:

Mansoor N, et al. Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials. Br J Nutr. 2016 Feb 14;115(3):466-79. 

The failure of low fat

A recent article in the prestigious journal The Lancet summarizes all major scientific trials on losing weight on low fat. The conclusion? There’s no evidence that low-fat helps to lose weight, compared to any other diet advice.

In fact, giving any other diet advice tends to be better, with people given the opposite advice (low carb, higher fat) in studies losing significantly more weight. Learn more 

The Lancet 2015: Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis

Bottom line

The latest review of all major trials of low carb diets show improved weight AND improvement of all major risk factors for heart disease:

Metabolic risk factors

Low carb clearly shows superior results for all the common features of the “metabolic syndrome”, i.e. weight, blood sugar, blood pressure and the cholesterol profile connected to metabolic dyslipidemia (HDL and triglycerides).

These factors are strongly connected to the risk of chronic disease like type 2 diabetes, heart disease, stroke, dementia and even cancer. So the fact that we can improve all of them with one single lifestyle intervention (reducing carb intake) is clearly incredibly important.

Overview of randomised controlled trials

Here’s an overview of the results of dozens of studies and meta-analyses comparing low-carb or low-fat diets, while tracking weight and other risk factors.

The blue (low carb) or red (low fat) squares signify a statistically significant advantage. The pale blue or red squares signify a non-significant trend toward low carb or low fat being superior.

trials image .png

As you can see above, low carb diets repeatedly beat low fat in all metabolic factors. On the other hand, low fat can result in somewhat lower total and LDL cholesterol.

However, since all the metabolic factors (including HDL) favor low carb, even the best measurements of cholesterol-associated risk (like total cholesterol/HDL) favor low carb, on top of the clear victory in blood pressure, blood sugar and weight (including waist measurements).

Links to references

Here are links to all the studies above, ordered from oldest to newest:

Brehm -03Foster -03Samaha -03Sondike -03Aude -04Volek -04Meckling -04Yancy -04Stern -04McAuley -05Nickols-R -05Dansinger -05Daly -06Truby -06Gardner -07Ebbeling -07Halyburton -07Dyson -07Westman -08Keogh -08Shai -08Tay -08Davis -09Bradley -09Volek -09Sacks -09Brinkworth -09Jenkins -09Frisch -09Elhayany -10Iqbal -10Lim -10Hernandez -10Yancy -10Foster -10Krebs -10Goldstein -11Summer -11Guldbrand -12Partsalaki -12Ruth -13Yamada -14Saslow -14Bazzano -14Tay -15Saslow -17Gardner -18.

Links to the meta-analyses:

Nordmann -06Hession -08Sackner-B -15Tobias -15Mansoor -16.The following compilation of studies to support a low carb diet has been taken from and is available at dietdoctor.com  There is more information including videos specifically for doctors and medical professionals at https://www.dietdoctor.com/low-carb/for-doctors