There has been a controversy over the last 30 years as to which is the best diet to prevent diabetes.
With over 90 million people in the U.S. with prediabetes, remission of prediabetes to normal is an important health concern, but one which has had little success in the past. This study’s objective was to determine the effect on remission of prediabetes with a high protein (HP) versus high carbohydrate (HC) diet, and effects on metabolic parameters, lean and fat body mass in prediabetic, obese subjects after 6 months of dietary intervention.
For this randomized controlled trial, they recruited and randomized 24 prediabetes women and men to either a high protein (30% protein, 30% fat, 40% carbohydrate; n=12) or high carbohydrate (15% protein, 30% fat, 55% carbohydrate; n=12) diet feeding study for 6 months. All meals were provided to subjects for 6 months with daily food menus for HP or HC compliance, and with weekly food pick-up and weight measurements.
At baseline and after 6 months on the respective diets, oral glucose tolerance and meal tolerance tests were performed with glucose and insulin measurements and dual energy X-ray absorptiometry scans.
There are several important findings of this study, which previously have not been reported. (1) The HP diet resulted in 100% remission of prediabetes to normal glucose tolerance, while the HC diet resulted in only 33% remission. To the best of the researchers’ knowledge, this is the first lifestyle intervention study where 100% remission of prediabetes was obtained. The results show that high efficacy can be achieved with dietary modification if parameters are rigorously controlled and monitored. (2) The HP group had greater improvement in insulin sensitivity, greater reduction in CVR factors, oxidative stress (ROS) and inflammation than the HC diet group. (3) The HP diet group’s percentage of lean body mass (LM) increased while percentage of body FM was decreased; whereas, the HC diet group lost percentage of both LM and FM. (4) There was no physical activity modification during the 6 months on the diets, and since all subjects were minimally physically active, researchers were able to study the direct effect of the HP versus HC diets. (5) Diet meals were given to each patient weekly at the CRC along with a survey of food consumption, which resulted in a high level of compliance.
The significance of this study is that reduction in caloric intake (without controlling micronutrient content) for weight loss has generally not been successful for remission of prediabetes (impaired glucose tolerance, IGT) to normal glucose tolerance (NGT).
We know that diabetic medications used to treat prediabetes are not without side effects and require long-term use. When you can get one hundred percent remission of prediabetes IGT to NGT using a high protein (HP) diet, but not a high carbohydrate (HC) diet, then we need to provide this information to the medical community.
The HC group sustained higher glucose and insulin levels with both the OGTTs and MTTs compared with the HP diet group after 6 months on the diet. The greater insulin response with the HC diet likely equates to greater β cells stress. The higher sustained glucose elevation with ingestion of glucose or higher glycemic foods as in the HC diet correlates with increased oxidative stress and inflammation in the HC group compared with the HP group, as the data showed. A study showed antioxidant enzymes induced by repeated intake of excess energy in the form of high-fat, HC diets are not sufficient to block oxidative stress and inflammation in healthy human subjects. Thus, the fact that the HP diet had a significantly greater reduction in ROS and inflammation markers than the HC diet in prediabetes subjects is of great health importance.
Although some studies have reported an HP diet can cause negative Ca balance, increased Ca loss in the urine and adversely affect the bone, the HP and HC diets contained more than the Food and Drug Administration (FDA) recommended amount of Ca/day and showed no bone loss or loss of Ca in the urine. The protein composition in this HP diet was 30%, which is at the upper limit of suggested protein consumption range (10–30%). This may not be at a high enough percentage to cause a negative Ca balance as has been reported.
Diet compliance is an important factor in macronutrient composition diet studies. Most studies rely on a patient’s recall via a food questionnaire of meals they ate days to weeks before, which is generally inaccurate. Strengths of this feeding study are that it was a randomized control trial where all food and daily diet plans were provided to each subject in the HP and HC diet groups at their weekly visit to the CRC along with a daily food consumption survey each week for 6 months. This monitoring resulted in >90% compliance of diet adherence. The study demonstrates for the first time that strict adherence of dietary intervention is possible and can produce meaningful and reliable results and remission of prediabetes. At an additional 6-month follow-up visit after 6 months on the diet study, the subjects who chose to stay on the HP diet plans, purchasing their own food and with consultations with the investigators when needed, maintained their weight loss and normal glucose levels.
The daily cost of such a diet (HP or HC) was about $13 a day with minimal personnel involvement (except for weekly pick-up of diet supplies).
- The HP diet resulted in 100% remission of prediabetes to normal glucose tolerance while the HC diet resulted in only 33% remission.
- This study demonstrates that strict adherence to dietary intervention with the HP diet is possible and results in remission of prediabetes to NGT.
- The HP group had greater improvement in insulin sensitivity, greater reduction in CVR factors, oxidative stress (ROS) and inflammation than the HC diet group.