Low Carb

The Science of Low Carb

The page below summarizes some of the science behind low-carb diets.

Read more about how low carb works here

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:

Saturated fat

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.

There were no clear effects of dietary fat changes on total mortality or cardiovascular mortality…

no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.

But wait, what about butter and other high fat dairy specifically? Well, actually people consuming it are if anything thinner and healthier than others:

The observational evidence does not support the hypothesis that dairy fat or high-fat dairy foods contribute to obesity or cardiometabolic risk…

This means that the scientific foundation of the low fat dietary advice has fallen. The reasons for it today are mainly economical (low fat high sugar products are very lucrative and finances a lot of lobbying), 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 it’s apparent to everybody.


Weight loss

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 19 modern scientific studies of the highest quality (RCT) that show significantly better weight loss with low carb diets:

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 DietObesity (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!

Feel free to let me know of any exceptions (or more examples) in the comments.


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

On the other hand, a meta-analysis of low-fat diets show that they tend to result in less weight loss:

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.

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.

The science of low carb

Dr. William Nancy - Is There Science to Support Low Carb? (SF 2016)4.4 out of 5 stars5 stars63%4 stars20%3 stars8%2 stars2%1 star4%68 ratings6824:04

Here is the opinion of a true expert on low-carb diets, Dr. William Yancy.


Low Carb Made Easy

Weight loss and low carb: Time to stop denying the science

Science for smart people


Keep reading about Success Stories on Low Carb



Improve this page

Do you have any suggestion – big or small – to improve this page?
Anything that you’d like added or changed?
Comment below or e-mail me at andreas@dietdoctor.com.


  1. Liah
    While I know low-carb has a bigger weight loss, that doesn't mean low-fat doesn't work. I don't have a link, but I recall a low-fat vs low-carb study that was done for a year. It clearly showed low carb had a bigger weight reduction in the first 6 months, but at the end of the trial the difference between low-fat and low-carb was not statistically significant anymore.

    In the end what really matters is the kind of diet you can follow for the rest of your life. Some people just aren't meat-eaters and they will have a harder time cutting their carbs than they will cutting their fats. Low fat, while the result is not as bit as low-carb, still reduces body weight and fat-mass, especially when combined with physical activity, as any diet should be.

  2. Brad
    Leah, thankfully there are many non meat fat sources for people to enjoy. Many are some form of dairy, so vegans will have some issues following it but buttered up veggies are an easy solution.
  3. Luz
    An important difference between low-carb and low-fat, for me, was that the higher-fat content of a low-carb diet means that I felt much more sustained, much less hungry. I used to eschew fat: I hated fat on meat as a child, and I still do. Later on, as a Type 1 diabetic, the diet recommended was high in carbs. This was considered ok because bread and oats and cereals were 'sugar-free'. (Ha!) I was led to believe that I should avoid butter and cream and even use hydrogenated (?) spray oils! Now I realise that carbs are not very sustaining and can, in some cases, lead to sugar-addiction and obesity. I've lost 35 pounds over 20 months on LCHF, and improved my mobility and flexibility.
  4. Hazel
    Regarding all the studies confirming that low carb "diet" is safe and effective in producing weight loss (I've lost 65 pounds), I think there still are many doctors who cling to the cholesterol theory that saturated fat causes heart disease. Their numbers are many and they're fiercely dogmatic. This may be the last hurdle of low carb supporters, but I think this needs to be addressed, not only because it's not true but also because the idea of eating fat seriously terrifies so many people who could be helped by eating the low-carb way but don't want to because their doctors are scaring them literally to death.

    Just a thought.

  5. terence
    What is perhaps the one best video presentation that summarizes the hard science behind LCHF? Not the empirical dietary studies of which there are many - I'm talking about the biochemistry behind how the body deals with various fats vs. various sugars and starches.
  6. Anjay
    You might be interested in this recent study also https://www.ncbi.nlm.nih.gov/pubmed/27680091
    "Our results do not support the association between CVDs and saturated fat, which is still contained in official dietary guidelines. Instead, they agree with data accumulated from recent studies that link CVD risk with the high glycaemic index/load of carbohydrate-based diets. In the absence of any scientific evidence connecting saturated fat with CVDs, these findings show that current dietary recommendations regarding CVDs should be seriously reconsidered."
  7. Michael
    Hello Andreas and Team, is it proper to use these 19 studies also to support specifically the Ketogenic Diet? Because the titles of them show, and your are mentioning too the Atkins diet, that they are mostly Low Carb and High Protein?..
    Reply: #8
  8. Michael
    ... So, an additional question: Why is the Atkins Diet also regarded as ketogenic, although it does not come with the protein restriction of the explicit "Ketogenic Diet"? (Or does it?)
    Thanks, Michael

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