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Obesity is a leading issue in American culture. More than one in three adults in the United States are considered obese, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Low-fat diets and low-carbohydrate diets are two popular strategies for weight loss.
A recent study done by researchers at the Stanford University School of Medicine assessed the effect of a low-fat versus a low-carbohydrate diet on the overweight adult population. It was found that there was no significant difference in weight change or insulation secretion pattern over the 12-month weight loss period. Past studies stated that weight loss for either diet group could range from about 25 kilograms lost to approximately five kilograms gained.
Led by researchers Christopher Gardner and John Trepanowski, the current study included 609 overweight individuals who were between 18 and 50 years old and body mass index (BMI) scores ranging from 28 to 40. For 12 months the participants were randomly assigned to either a healthy low-fat diet or a healthy low-carbohydrate diet.
Over the course of 12 months, the participants in the study were required to attend 22 diet-specific small group sessions that explained ways to achieve the lowest fat or carbohydrate intake long-term. Professional dietitians led each class.
The dietary interventions included participants reducing intake of total fat or carbohydrates to 20 grams per day in the first eight weeks.
In addition, the low-fat group was instructed to steer clear of edible oils, fatty meats, whole-fat dairy and nuts, while the low-carbohydrate group needed to remove cereals, grains, rice, starchy vegetables and legumes from their diet.
All participants were asked to maximize vegetable intake while minimizing sugar and trans fat intake.
At the end of the 12 months, the mean weight change for the healthy low-fat diet group was -5.3 kilograms and minus six kilograms for the healthy low-carbohydrate group. This was found not to be statistically significant. In other words, there was no significant difference in terms of weight loss between the two groups. Within each group, participants had a similar range of weight change (-30 to 10 kilograms).
In addition, both diets improved lipid profiles and lowered blood pressure, insulin and glucose levels. However there was no significant difference between groups.
A glucose tolerance test was used to measure insulin sensitivity.
Insulin sensitivity is often used in dietary studies as a measure of how well people respond and adhere to diets.
At the end of the study it was found that the low-fat group consumed 29 percent of their calories from fat (versus 45 percent in the low-carbohydrate group). In other words, the majority of these subjects did adhere to the diet. Similarly the low-carbohydrate group consumed 30 percent of their calories from carbohydrates (versus 48 percent in the low-fat group).
While the participants were not asked to count the calories they ate day to day, researchers found that the average participant actually reduced their caloric intake by about 500 to 600 calories each day.
The researchers from the study noted that the conclusion to this study is that there is not one “best” diet for a population. The study shows the success of long-term diets with slow and steady changes, but provides little evidence for whether a low-fat or low-carbohydrate diet is more successful for weight loss.