Many nutritionalists and dietitians are joining the chorus of fans of ketogenic diet. And certainly it is more effective that even the best diet pills like Garcinia Cambodia.
However, there are some health professionals concerned about the use of ketogenic diets for diabetics.
Addressing this concern, a recent randomized controlled trial investigated the safety, tolerability and effectiveness of a 4-month, very low-calorie ketogenic diet in 89 obese people with type 2 diabetes.
Here is a detailed summary of its findings, in addition to some background information.
The ketogenic diet contains minimal amounts of carbs.
This forces the body to burn fat and leads to ketosis, which is characterized by elevated levels of ketone bodies in the blood. The ketone bodies partially replace glucose (blood sugar) as fuel for cells.
Reducing sugar intake has multiple health benefits, especially for diabetics.
For these reasons, high sugar intake is probably one of the main causes of weight gain and obesity.
A ketogenic diet eliminates most dietary sugar, as well as the health problems associated with it. However, eliminating dietary carbs means that you have to eat more fat or protein instead.
Increasing fat intake doesn’t seem to be a problem if the diet is also calorie-reduced. Studies indicate that high-fat diets are more effective for weight loss than low-fat diets. This is probably because high-fat diets contain much fewer carbs (1).
Others have pointed out that very low-carb or high-protein diets may not be feasible in a real-life setting (6).
In 2008, the American Diabetes Association even concluded that very low-carb diets were of limited use for people with diabetes and should only be considered as part of a structured weight loss program (7).
However, few studies have examined the safety and effectiveness of a calorie-reduced, very low-carb ketogenic diet, compared to a standard weight loss diet.
This study examined the safety and effectiveness of a low-calorie ketogenic diet in obese diabetics.
This randomized controlled trial evaluated the safety, tolerability and effectiveness of a low-calorie ketogenic diet in obese people with type 2 diabetes.
A total of 89 men and women, aged 30–65, participated in the study. They followed a 4-month weight loss program, which included lifestyle and behavioral modification support.
The participants were randomly assigned to one of two groups:
1. Very Low-Calorie, Ketogenic Diet (VLCK)
This was a commercial weight loss program (DiaproKal Method) based on specific protein supplements provided by Pronokal Protein Supplies in Spain.
The program consisted of three stages:
- Active phase: Very low-calorie diet (600–800 calories per day) containing less than 50 grams of carbs from vegetables and 10 grams of olive oil. Protein intake ranged between 0.36–0.55 grams per pound of body weight (0.8–1.2 g per kg).
- Metabolic stabilization: When the participants had reached a pre-specified weight loss target, they began a low-calorie diet and gradually started to incorporate different food groups.
- Maintenance phase: Finally, the participants went on a weight maintenance diet that was balanced in carbs, protein and fat and ranged between 1,500–2,250 calories per day.
2. Standard Low-Calorie Diet (Control)
This was a standard weight loss diet based on the American Diabetes Association Guidelines (8).
It aimed at reducing calorie intake by 500–1,000 calories per day, depending on the participants’ basal metabolic rate.
The diet provided 10–20% of calories from protein, 45–60% from carbs and less than 30% of calories from fat.
In both groups, the participants attended nine individual support sessions with a dietitian and were contacted by telephone twice a month.
The researchers measured the participants and took blood samples on four occasions: 1) at the start of the study, 2) after 2 weeks, 3) after 2 months, and 4) at the end of the study (after 4 months).
They measured the following parameters:
- Renal function: Biomarkers of kidney function were measured in blood samples.
- Liver function: Biomarkers of liver function were measured in blood samples.
- Ketones: Levels of ketone bodies in blood samples were measured to confirm that those in the VLCK reached ketosis.
- Body weight, body mass index and waist circumference.
- Blood sugar control: Fasting blood sugar, insulin and HbA1c were measured in blood samples. Insulin resistance was calculated using the homeostasis model assessment (HOMA).
- Blood lipids: Fasting triglycerides, total cholesterol and LDL cholesterol.
- Dietary adherence: Assessed using the Eating Self-Efficacy Scale.
Conclusion: This was a randomized controlled trial examining the safety and effectiveness of a calorie-reduced, very low-carb ketogenic diet in obese people with type 2 diabetes.
Finding 1: The Ketogenic Diet Caused Greater Weight Loss
The participants in the VLCK group lost an additional 22 lbs (10 kg) of body weight, compared to the control group.
Specifically, they lost 32 lbs (15 kg) in the VLCK group and 11 lbs (5 kg) in the control group.
They also experienced a greater decrease in waist circumference, as shown in the chart below.
Some researchers have speculated that the ketogenic diet helps people lose weight only because it’s much higher in protein than the standard weight loss diet.
One study suggests that going on a ketogenic diet without increasing protein intake has no lasting effect on the amount of calories burned and doesn’t lead to additional weight loss, compared to a standard, high-carb weight loss diet.
Conclusion: The ketogenic diet led to significantly greater weight loss than the standard low-calorie diet.
Finding 2: The Ketogenic Diet Led to Greater Improvements in Blood Sugar Control
Insulin resistance decreased significantly more in the VLCK group, compared to the control, as shown in the chart below.
Fasting blood sugar levels reduced similarly in both groups.
However, the decrease in HbA1c was significant only in the VLCK group. HbA1c is a marker of blood sugar control that represents the previous 3-month average of blood sugar levels.
Conclusion: The ketogenic diet significantly improved blood sugar control, compared to a standard weight loss diet.
Finding 3: Self-Reported Adverse Effects Were More Common on the Ketogenic Diet
The researchers detected no significant differences in safety parameters between groups. However, self-reported adverse effects were more common in the VLCK group.
Mild adverse effects were reported by 80% of the participants in the VLCK group but only 41% of those in the control group. These included headache, nausea, vomiting and weakness.
Additionally, constipation and low blood pressure when standing up (orthostatic hypotension) were more common in the VLCK group at the end of the study. No serious adverse effects were reported.
Adverse effects became less frequent as the study progressed. The authors concluded that the ketogenic diet is a safe, well-tolerated weight loss method for people with type 2 diabetes.
The adverse effects reported in this study are similar to those generally associated with very low-carb diets (11).
Conclusion: Blood analyses revealed no significant differences in biomarkers of liver and kidney function between groups. However, self-reported adverse effects were more common in the VLCK group.
Participants in the VLCK group received protein supplements provided by Pronokal Protein Supplies in Spain.
Additionally, five of the nine authors received research grants and advisory board fees from the company, creating a conflict of interest.
Otherwise, the study appears to have been well designed.
Summary and Real-Life Application
In conclusion, a weight loss program based on the ketogenic diet was significantly more effective than a standard weight loss program.
It appeared safe and reasonably well tolerated by people with type 2 diabetes and caused greater weight loss and improvements in blood sugar control.