Low-carbohydrate diets have a long history of therapeutic use for obesity, diabetes and epilepsy.
Millions of people all around the world have tried such a diet, usually with good results.
Despite that, nutritionists and health authorities do not recommend such a diet and in fact claim that it is dangerous.
They claim that low-carb diets don’t have scientific evidence behind them and often refer to them as “fad diets.”
With this article, I plan to prove them wrong.
It is true that 10 years ago low-carbohydrate diets didn’t have any major scientific evidence behind them.
But since the year 2003, at least 21 randomized controlled trials have been performed on humans.
Ask anyone with a background in nutrition, public health and medical science, and they will tell you that randomized controlled trials are the gold standard to prove safety, cause and effect.
Here I will review each one of those 21 trials. All of these are published in respected, peer-reviewed research journals such as the New England Journal of Medicine, American Journal of Clinical Nutrition and Nature.
There was no cherry picking of data here.
I have specifically asked nutritionists that are against the use of low-carb diets to find me controlled trials that demonstrate that they are either ineffective or unsafe, but the fact is that such trials do not exist.
All the studies are randomized controlled trials comparing a low-carb diet to the standard calorie restricted low-fat diet that is generally recommended by health professionals.
I do not believe that any one diet plan is perfect for everyone. The best diet plan is the one that an individual can follow in the long term to make it a permanent lifestyle change.
However, I want the media, the public as well as professionals to acknowledge low-carb diets as a viable option for those with obesity or other symptoms of the metabolic syndrome (which are the biggest health problems in the world).
People should be given the choice, especially when all the scientific evidence suggests that low-carb is easier, healthier and more effective than the calorie restricted, low-fat diet that is generally recommended, despite overwhelming contrary evidence.
Details: 63 obese men and women, randomly assigned to either a low-carb, high fat Atkins diet or a conventional low-fat diet. Low-fat group is calorie restricted. Outcomes measured are weight loss and cardiac risk factors.
Weight Loss: Greater on the low-carb diet at 3 months (-6.8% vs. –2.7%) and 6 months (–7.0% vs. –3.2%). Difference not statistically significant at 12 months (–4.4% vs. –2.5%).
Cardiac Risk Factors: Increase in HDL and decrease in Triglycerides on low-carb diet. Also an increase in Total and LDL cholesterol at 3 months, compared to the low-fat diet, but not statistically significant at 6 and 12 months.
Details: 132 severely obese subjects with a mean body mass index of 43. High prevalence of diabetes (39%) and the metabolic syndrome (43%). Assigned to a low-carb diet or a low-fat, calorie restricted diet.
Weight Loss: Greater weight loss on the low-carbohydrate diet at 2, 4 and 6 months. Weight loss at 6 months was -5.8kg on the low-carb diet vs. -1.9kg on the low-fat diet.
Risk Factors: Greater improvements on the low-carb diet for triglycerides, insulin sensitivity, blood glucose levels. Insulin levels in non-diabetic subjects improved on a low-carb diet. Results for HDL, LDL and Total Cholesterol were not statistically significant.
Details: 30 overweight adolescents randomized to either a low-carb or a low-fat diet for 12 weeks. Neither group is calorie restricted.
Weight Loss: The low-carb group lost an average of 9.9kg, while the low-fat group lost 4.1kg.
Risk Factors: Greater improvements on the low-carb diet for triglycerides and non-hdl cholesterol. Greater improvements in Total and LDL cholesterol in the low-fat group. No statistically significant results for HDL cholesterol.
Details: 53 obese women randomized to two groups: a low-carb diet group and a low-fat diet group, for 6 months. Low-fat group is calorie restricted.
Weight Loss: The low-carb group lost more weight (8.5kg) compared to the low-fat group (3.9kg) at 6 months.
Risk Factors: At 6 months, both groups had increased HDL cholesterol. Triglycerides decreased substantially in the low-carb group, but remained the same in the low-fat group. LDL and total cholesterol didn’t change much in either group at 6 months.
Details: 60 participants were randomized to either a modified low-carb diet or a low-fat diet based on the National Cholesterol Education Program. Both groups are calorie restricted.
Weight Loss: The modified low-carb group lost an average of 13.6lb (6.2kg) while the low-fat group lost an average of 6.1lb (2.8kg).
Cardiac Risk Factors: There were no significant differences in blood lipids between groups. The modified low-carb group decreased total cholesterol, triglycerides, and percentage of dense LDL while increasing LDL particle size. The low-fat group decreased total, HDL and LDL cholesterol.
Details: 119 obese and hyperlipidemic individuals randomized to either a low-carb, ketogenic diet or a low-fat diet. Low-fat group was calorie restricted.
Weight Loss: Group on the low-carb diet lost an average of 12.0kg, while the low-fat group lost an average of 6.5kg.
Risk Factors: Triglycerides decreased and HDL cholesterol increased on the low-carb diet. Total cholesterol and triglycerides decreased on the low-fat diet. There was a significant difference between groups for triglycerides and HDL, in favour of the low-carb diet.
Details: 28 overweight/obese men and women are randomized to either a calorie restricted low-carb diet or a calorie restricted low-fat diet. The low-carb group ends up eating about 300 calories more per day. Outcomes measured are weight loss, body composition, trunk fat mass and resting energy expenditure.
Weight Loss: The low-carb group lost more weight than the low-fat group, despite eating more calories. The men lost more weight than the women. The ratio of trunk fat/total fat also decreased during the low-carb diet (trunk fat, or abdominal fat, is the worst).
Other outcomes measured: Resting energy expenditure did not decrease on the low-carb diet, but it did decrease on the low-fat diet. The loss of fat in the trunk region was three times greater on the low-carb compared to the low-fat diet.
Details: 40 overweight and obese men and women randomized to either a low-carb or a low-fat diet. The calories in the low-fat group were matched to the calories in the LC group, although the LF group eventually ate a bit less. Study went on for 10 weeks.
Weight Loss: Both groups lost a similar amount of weight. LC lost 7.0kg and the LF group lost 6.8kg. No statistically significant difference.
Risk Factors: Total and LDL cholesterol remained unchanged in the LC group but decreased in the LF group. HDL decreased in the LF group and increased in the LC group. Both groups lowered their triglyceride levels.
Details: 28 overweight/obese premenopausal women were placed on either a low-carb/high-protein or a high-carb/low-fat diet for 6 weeks. Primary outcomes measured were hunger and cognitive eating restraint. High-carb/low-fat group was calorie restricted.
Weight Loss: The women on the low-carb/high protein diet lost more weight (5.7% of body weight) compared to the high-carb/low-fat group (3.3% of body weight).
Outcomes Measured: The LC/HF group of women had less hunger than the HC/LF group, but both groups exhibited similar cognitive eating restraint (CER).
Details: 102 type II diabetics randomized to either a low-carb or a low-fat diet. Study went on for three months. Main outcomes measured were weight, glycaemic control, lipids and blood pressure. The low-fat group was instructed to reduce portion sizes.
Weight Loss: The LC group lost more weight, -3.55kg, while the LF group lost 0.92kg.
Other Outcomes Measured: The ratio of Total cholesterol:HDL improved on the LC group. Triglycerides, Systolic blood pressure and HbA1c (a marker for blood glucose levels) also decreased on the LC diet, but the difference was not statistically significant compared to the low-fat diet.
Details: 119 overweight individuals randomized to either a low-carb, ketogenic diet or a calorie restricted low-fat diet for 6 months. Main outcomes measured are mood, hunger and other self reported symptoms.
Weight Loss: The LC group lost 12.9kg, while the LF group lost 6.7kg.
Other Outcomes Measured: The LC group had significantly better mood (less negative affect) and less hunger than the LF group.
Details: 311 overweight/obese premenopausal women assigned to either an Atkins, Zone, LEARN or Ornish diet for 12 months. Zone and LEARN were calorie restricted, Atkins and Ornish were not.
Weight Loss: Weight loss was greatest at 12 months in the Atkins group (-4.7Kg) compared to the LEARN (-2.6Kg), Zone (-1.6Kg) and Ornish group (-2.2kg).
Risk Factors: Triglycerides decreased and HDL increased on the Atkins diet. LDL cholesterol favoured the LEARN and Ornish (low-fat) groups at 2 months, but the effects dimished at 6 and 12 months. Systolic blood pressure was significantly lower in the Atkins group at 12 months compared to the other groups, and diastolic blood pressure significantly lower than the Ornish (very low fat) group.
Details: A low-carb diet compared to a low-fat diet in 93 overweight or obese individuals for 8 weeks. Outcomes measured were weight loss, mood and cognitive function. Both groups were calorie restricted.
Weight Loss: The LC group lost more weight, 7.8kg, compared to the LF group which lost 6.4kg.
Other Outcomes: Both LC and LF groups had significant improvements in mood, with no difference between groups. Both groups improved cognitive function. Speed of processing improved less in the LC group.
Details: 13 diabetic and 13 non-diabetic individuals randomized to either a low-carb or a low-fat diet for 3 months. Main outcomes measured are body weight, glycated hemoglobin (HbA1c), ketone and lipid levels. Low-fat group was calorie restricted.
Weight Loss: The LC group lost 6.9kg while the low-fat group lost 2.1kg.
Other Outcomes Measured: There was no statistically significant difference in any of the other parameters.
Details: 322 moderately obese individuals randomized to either a low-fat calorie restricted diet, a mediterranean calorie restricted diet or a low-carb non-restricted diet for 2 years.
Weight Loss: The LF group lost 2.9kg, the mediterranean group lost 4.4kg and the LC group lost 4.7kg.
Risk Factors: The LC group improved both HDL and Triglycerides, and the ratio of Total:HDL cholesterol, compared to the other groups.
Details: 84 obese and type II diabetic individuals randomized to either a low-carb ketogenic diet or a low glycemic index calorie-restricted diet for 3 months.
Weight Loss: The LC group lost 11.1kg and the LF group lost 6.9kg.
Other Outcomes Measured: The LC group had more improvements in HbA1c and High-Density Lipoprotein. Diabetes medication were reduced or eliminated in 95.2% of the LC group, compared with 62% of the low glycemic index diet.
Details: 107 individuals randomized to either a very low-carbohydrate diet or a low-fat diet for 8 weeks. Both groups were calorie restricted. Main outcomes measured were markers of endothelial function and cardiovascular disease risk.
Weight Loss: The LC group lost more weight, 7.5kg, compared to the LF group which lost an average of 6.2kg.
Risk Factors: There was no difference between groups on endothelial function. The LC group had further improvements in Triglycerides and HDL, compared to the low-fat group.
Details: 88 obese individuals randomized to either a low-carb, high-fat diet or a high-carb, low-fat diet for 6 months. Both groups were calorie restricted. Main outcomes measured were weight loss and cardiac risk factors.
Weight Loss: The LC group lost 11.9kg and the LF group lost 10.1kg. The difference between groups was not statistically significant.
Cardiac Risk Factors: Triglycerides and HDL improved further in the LC group, while Total and LDL cholesterol improved in the LF group. 24% of individuals on the low-carb diet increased LDL cholesterol by 10% or more.
Details: 40 subjects with atherogenic dyslipidemia randomized to either a low-carb or an isocaloric low-fat diet for 12 weeks. Main outcomes measured were markers of the metabolic syndrome.
Weight Loss: Despite a similar reduction in calories, the low-carb group lost double the amount of weight as the low-fat group (10.1kg vs. 5.2kg).
Risk Factors: The LC group showed more favourable improvements in triglycerides, HDL, Triglyceride:HDL ratio. The LC group also had more improvements in fasting glucose, fasting insulin and a reduction in small LDL particles.
Details: 118 obese individuals randomized to either a low-carb or a low-fat diet for 12 months. Both groups were calorie restricted.
Weight Loss: The LC group lost 14.5kg of weight, while the LF group lost 11.5. The difference was not statistically significant.
Risk Factors: Compared to the LF group, the LC group increased HDL, Total and LDL cholesterol and decreased triglycerides.
Details: 46 severely obese adolescents randomized to either a low-carb, high-protein diet or a calorie-restricted low-fat diet for 13 weeks.
Weight Loss: The LCHP group lost significantly more weight and had a significant reduction in the BMI-z score compared to the LF group.
Risk Factors: Both groups improved Total cholesterol and LDL cholesterol levels. HDL levels decreased in the LF group, while Triglycerides decreased in the LC group.
I went through all of the studies, took me about a week.
Weight Loss on Low-Carb vs. Low-Fat Diets
Weight loss is, almost without exceptions, greater on low-carb diets although the difference isn’t always statistically significant.
This effect is especially evident when the low-carb group is allowed to eat until fullness while the low-fat group is calorie restricted, which is how these diets are usually prescribed in practice.
When both groups eat the same amount of calories (isocaloric), the low-carb groups still tend to lose more weight but the effects aren’t large enough to reach statistical significance.
Part of the reason for greater weight loss on the low-carb diet given that calories stay the same may be increased water loss.
Calories, Carbs, Fats and Protein
When the low-carb group is not calorie restricted but the low-fat group is, they tend to end up eating a similar amount of calories. Interestingly, calorie restricted low-fat dieters also end up eating a lower total amount of carbohydrates.
Another interesting observation is that on a low-carb diet, people don’t necessarily end up eating more fat than they used to. In fact, they tend to eat similar amounts of fat as they were before starting the diet.
Protein intake is higher on the low-carb diet, which may explain some of the increased satiety.
Appetite And Hunger
Low-carb diets tend to decrease appetite and hunger.
This is the main reason people lose so much weight without portion control or calorie restriction, they simply don’t want to eat as much.
Compliance and Attrition Rates
The studies where the LC diets are most effective are where people manage to follow them completely and restrict carbohydrates accordingly.
However, as with every weight loss diet, compliance is an issue and people tend to increase their carb intake over time. As carb intake increases, weight loss tends to slow down and some people even start gaining weight back.
This implies that weight loss on a LC diet (as with any diet, really) requires people to stick with it for life.
Attrition rates tend to be lower on LC diets (more people make it to the end) despite arguments by dietitians about LC diets being harder to stick to because they eliminate entire food groups.
This is probably due to the fact that people can eat until fullness and don’t have to be hungry all the time, which is common with calorie-restricted low-fat diets
The idea that low-carb diets are harder to follow is a myth!
LDL and Total Cholesterol levels
Low-fat diets tend to decrease both Total and LDL cholesterol, but mostly in the first 3 months or so. Then they tend to go back up.
It is not true that low-carb diets raise LDL or Total cholesterol levels. The fact is that they remain pretty much the same. They don’t get any higher than before, although there is some individual variation here.
This is probably nothing to worry about, as low-carb diets tend to change the LDL pattern from small, dense LDL to large, fluffy LDL which is benign.
HDL Cholesterol levels
HDL cholesterol (the “good” cholesterol) usually goes up substantially on a low-carb diet, while it tends to increase less or even go down on a low-fat, high-carb diet.
Blood triglycerides always go down on low-carb diets, while they tend to decrease less, stay the same or go up on calorie-restricted low-fat diets.
Blood pressure seems to decrease for both low-carb and low-fat dieters and the difference usually isn’t significant between groups.
Glucose, Insulin and Type II Diabetes
Glucose and insulin tend to decrease further on low-carb diets in non-diabetics, but it is not always statistically significant.
In type II diabetics, glucose and insulin levels decrease much more on low-carb diets and the patients are often able to eliminate or drastically reduce medication.
This implies that these diets may be particularly useful for those with diabetes or impaired glycemic control.
There are some mild side effects of low-carb, ketogenic diets that are usually over in a few days. These include headache, nausea, fatigue, insomnia and constipation.
There are NO serious adverse effects of low-carb, ketogenic diets, despite the scare tactics (lies)!
Time to Retire The Fad
Low-carb, ketogenic diets are superior to low-fat diets, not only when it comes to weight loss but also in improving pretty much all the major risk factors for western disease.
The results of the studies above all point to low-carb diets being superior when compared to low-fat diets. This is especially prominent for obese individuals, diabetics and those with the metabolic syndrome.
Low-carb diets lead to much more weight loss than the standard of care, low-fat calorie restricted diets, without causing hunger. This is important, because being hungry all the time has a significant effect on quality of life and is hard to sustain.
Low-carb diets also improve other risk factors for disease further than low-fat diets, especially Triglycerides, HDL and LDL pattern.
Low-carb diets are the easiest, healthiest and most effective way to lose weight and reverse metabolic disease. This is a scientific fact.
It is time to retire the low-fat fad!