Low carb nutrition for weight loss is is currently a very popular concept. But is there any scientific evidence that shows low carb or ketogenic diets are superior to others?

From Fat To Carbs

For the last 50 years, the anti-fat dietary paradigm has dominated. Now, as people broaden their knowledge about nutrition, the goal-posts have been moved. The current obsession is with carbohydrates, or, more specifically, the low-carbohydrate diet. First championed into fame by the late Robert Atkins, and later perpetuated into utter idiocy by current diet commentators to the likes of Gary Taubes. This article has the sole intention to examine low-carbohydrate diets and their purported acceleration of fat-loss in isocaloric diets. Also discussed is the brother of low-carbohydrate, the ketogenic diet.

Low Carb, High Folly

The belief holds that if one restricts carbohydrate intake, insulin will subsequently be restricted and thus fat deposition will ultimately be reduced. A number of glaring problems arise when one looks at this in its totality. It completely disregards the fundamental precept of weight-regulation, the calorie in, calorie out model.

Studies observing weight-loss in individuals on isocaloric regimens are of varying quality. There is the ‘free-living’ study, which are basically uncontrolled, observational studies which are notoriously inaccurate in their food intake reporting. Then there is the controlled trial, or most commonly seen in dietary experimentation – metabolic ward trials. These feeding studies involve institutionalized subjects who are confined to a hospital or research facility. These types of studies are fastidious in their control and offer a level of qualitative superiority that free-living studies cannot touch.

Since 1955, metabolic ward trials have failed abysmally to support the contention that low-carbohydrate, isocaloric diets have resulted in statistically significant greater fat-derived weight loss than high-carb diets (Table 1). In other words, they don’t work.

Only studies with a duration either equal to or longer than 3 weeks will be analysed. Short-term studies generally tell us little compared to longer term studies which allow a holistic assessment rather than a mere myopic overview.

Metabolic Ward Feeding Trials of Isocaloric Diets with Different Carbohydrate Quantities Study Author(s)

Carbohydrate Content (either grams or %cal) Duration (days) Statistically significant difference in weight/fat loss for the low-carbohydrate regimen? (1) Werner, 1955 52g vs 287g 21 NO (2) Olesen & Quuade, 1960 50% vs 18% 21 NO (3) Pilikington et al., 1960 75% vs 13% and 91% vs 9% 24 NO (4) Kinsell et al., 1963 3% vs 64% 21 NO (5) Krehl et al., 1967 Widely varying over 10 dietary periods in 3 groups of subjects. 28 NO (6) Bortz et al, 1967 90g vs 0g vs 160g 24 NO (7) Bortz et al., 1968 1. 52g vs 120g vs 0g 2. 80g vs 0g 24 NO (8) Grey & Kipnis, 1971 62% vs 25% 21 NO (9) Grey & Kipnis, 1971 72% vs 0% 28 NO (10) Rabast et al., 1979 170g vs 25g 30 YES

(11) Rabast et al., 1979 355g vs 48g 25 NO (12) Rabast et al., 1981 225g vs 40g 28 YES

(13) Bogardus et al., 1981 36% vs 1% 42 NO (14) Hoffer et al., 1984 38g vs 0g 56 NO (15) Hendler et al., 1988 2% vs 55% 21 NO (16) Baggio et al., 1988 46% vs 56% 21 NO (17) Brinton et al., 1990 43% vs 76% 28 NO (18) Leibel et al., 1992 75% vs 45% 28 NO (19) Vazquez & Adibi, 1992 76g vs 10g 28 NO (20) Vazquez & Kazi, 1995 9g vs 86g 28 NO (21) Vazquez et al., 1995 10g vs 76g vs 86g 28 NO (22) Piatti et al., 1994 30% vs 60% 21 NO (23) Golay et al., 1996 15% vs 45% 42 NO (24) Miyashita et al., 2004 39% vs 62% 28 NO (25) Stimson et al., 2007 4% vs 35% 28 NO (26) Gately et al., 2008 55% vs 47% 28 NO

Even just a superficial reading of the table shows the clear absence of evidence supporting the low-carbohydrate diet for fat loss. It offers no observable advantage over diets higher in carbohydrate or any other macronutrient.

Rabast et al. reported supportive findings for a low-carbohydrate diet (10,12) but there is much doubt over these conclusions. In the first of these studies obese patients that followed the low-carbohydrate diet lost an extra 2.3KG. The authors remarked, “…an increased rate of metabolism presents itself as the most feasible explanation.” And in the second study subjects on the low-carbohydrate diet lost an average of 2.45KG more than the high-carbohydrate group, and again the authors were quick to ascribe this to an ‘increased metabolism’.

Weak Studies

A closer analysis of these papers reveals perplexing abnormalities that significantly weaken the case for these two studies. Foremost, there was an unusually high dropout rate, which in the 1979 study was to the figure of 40%. In ward studies, where supervision and support are emphatically implemented, dropout rates are traditionally non-existent to minimal. The authors offer absolutely no explanation for this huge attrition. This surely had an effect on study results; it can be clearly observed in the paper that results fluctuated between statistically significant (on day 30) and not statistically significant (5 days earlier).

The authors’ claim that an increased metabolism explained the difference in weight-loss, however this runs opposite to the very fact that they did not measure metabolic rate at all. And moreover, tightly controlled studies have shown no greater increase in metabolic rate or dietary-induced thermogenesis (DIT) on low-carbohydrate meals or diets(27,28,29,30,31,32,33,34,35,36). Ultimately, the many discrepancies and overwhelming weight of conflicting evidence cast aspersions on the validity of the studies conducted by Rabast et al.

The perceived effectiveness of low-carbohydrate dieting comes from the dramatic inital weight-loss. And indeed, many of these studies have found weight-loss to be accelerated in the first 1 to 2 weeks on a low-carbohydrate regimen. However, this is nothing more than fluid-loss via glycogen depletion (37) which is particularly exacerbated on low-carbohydrate diets(38, 39).

Corroborating the findings of ward studies, long-term free-living studies have also investigated the claims of faster fat-loss on a carbohydrate restricted diet. Results have shown similar endpoint weight-losses with widely varying carbohydrate content (40,41,42,43,44,45,46,47,48,49,50).

As far as any expediting effects on fat-loss go, low-carbohydrate diets offer nothing as clearly demonstrated. Despite this, low-carbohydrate diets need to be be appreciated for their powerful satiating effects through glucostatic mechanisms (51, 52), increased CCK-8 secretion from possibly higher fat intakes (53,54,55) and similar hunger suppression and appetite control exerted by possibly higher protein intakes (56, 57,58,59).

Calories, Not Carbohydrates



Perhaps the best summation of the low-carbohydrate diet comes from the conclusion in the Krehl et.al paper – “The wide appeal of carbohydrate restricted diets may relate to the fact they offer something different, are generally more permissive than the usual dietary programs for weight-reduction. and in the initial loss of weight is quite significant as a result of diuresis of salt and water; this is not related to an increased catabolism of fat and hence is artifactual. [The] continued and sustained loss of adipose tissue depends in the final analysis on prolonged restriction of calories, whether these are derived from fat, carbohydrate, or protein.” (5)

If carbohydrate-restriction had any extra beneficial effects on fat loss this should be easily reproducible in studies and well documented in the literature. Decades of closely controlled, metabolic ward feeding trials have clearly refuted this. The ‘low-carb mania’ is kept alive with the selective citation of unreliable and sub-par quality, short-term free-living studies. The amassed research presents the clear conclusion that it is unequivocally calories, not carbohydrates that dictates weight regulation.

Ketogenic Diets – Equally As Useless, Twice As Stupid



The ketogenic diet is conventionally a high-fat, moderate-to-high protein and very low-carbohydrate eating regimen. It’s sole purpose is to induce the state of ketosis, where the body derives fuel from fatty acids and ketone bodies rather than glucose.

Much to the chagrin of ketogenic diet exponents, metabolic ward trials have routinely failed to support the notion that ketogenic diets accelerate fat loss (4,6,7,9,13,14,15,19,20,21).

Requiring further investigation are the numerous adverse health effects. It is commonly touted that ketogenic regimens have been used successfully in epileptic persons for the better half of 90 years and this attests to the safety of such a diet. Indeed, it has been a tool employed to treat refractory epilepsy however this is not without its problems.

Ketogenic diets have been associated with lethargy, halitosis (bad breath), constipation(60, 61) , menstrual irregularities (62,63), a higher excretion of sodium, potassium (64) and selenium (65, 66), deteriorated mood and cognition (67,68,69,70), dehydration, cardiomyopathy, bruising, diarrhea, nausea and vomiting, gastritis and constipation, vitamin and mineral depletion, hepatitis, pancreatitis, metabolic acidosis, gout, bone mineral deficiency, kidney stones and hypoglycemia (71,72,73,74,75,76,77).

It makes little sense to follow a diet that offers no benefit to fat-loss all while incurring a multitude of possible adverse health implications.

Calories Are King

Those who claim superiority for the low-carbohydrate and ketogenic diet have either not bothered to review the literature, or they remain completely ignorant of it. As illustrated, quality research since the 1950s does not support the role of the low-carbohydrate or ketogenic diet in fat-loss any more than a low-protein or low-fat diet. Despite the dogmatic low-carb guru’s who vehemently defend their scientifically untenable position, you as the reader are capable of drawing your own conclusions based on the existing evidence. Calories have always been, are, and forever will be the only determinant of absolute weight regulation.

Final Words

While I wholly acknowledge that carbohydrate-restricted diets work and have produced weight-loss for millions of people worldwide, this article is solely addressing the claim that they accelerate the weight-loss process through some magical metabolic effect. Yes, low and no-carbohydrate works, but (metabolically) no more than any other isocaloric diet.

This is part 1 in a series of articles called ‘Disrobing Dogma’, which tackles the widely propagated and hugely popular dogmatic diet and nutrition claims that actually have no basis in scientific reality. I am also pleased to be on board here at evilcyber.com, hopefully I can contribute information of value to the public while also allowing myself to sharpen my writing skills and further my own knowledge. Thank you for reading.

Pictures courtesy of “Like_the_Grand_Canyon“, “admiller“, Cam Switzer and “bigbirdz“.