The number of different diets available can make a person dizzy. Two popular types are low fat diets and low carbohydrate diets. Is one better than the other?
A recent study found that individuals on very low carbohydrate diets lost a little more weight than those on low fat diets over the long-term.
Those on the very low carbohydrate diets also reduced their diastolic blood pressure (bottom number) more than those on the low fat diets did.
However, both the "good" and "bad" cholesterol levels increased more for those on the very low carbohydrate diets as well.
The authors concluded that very low carbohydrate diets may be a good option for fighting obesity.
The study, led by Nassib Bezerra Bueno, a researcher in the nutrition department at the Federal University of Alagoas in Brazil, compared two different types of diets for long-term weight loss.
One type of diet studied was a very low carbohydrate "ketogenic" diet in which individuals ate no more than 50 grams of carbohydrates a day.
This is a diet similar to Atkins, South Beach and others that dramatically cut carbohydrates so that the body produces "ketones."
Ketones are produced when the body is forced to break down and burn fat because energy from carbohydrates are not available.
The other diet type studied in this research was a low fat diet. A low fat diet was defined as one in which less than 30 percent of overall calories come from fat.
The authors searched eight databases for all randomized controlled trials through August 2012 that compared very low carbohydrate diets and low fat diets for at least one year of follow-up.
The authors primarily looked at the weight loss in both groups, but they also looked cholesterol levels, blood pressure, insulin levels, blood sugar and a few other biological markers of cardiovascular health.
The researchers found 13 studies involving a total of 1,577 participants, with 787 assigned to a low fat diet and 790 assigned to a very low carbohydrate diet.
When the researchers analyzed all these results together, they found that participants on very low carbohydrate diets lost more weight than participants on low fat diets.
The amount lost, however, was very small. The average amount of weight lost by those on very low carbohydrate diets over the long-term was two pounds.
The results were better in the short-term analysis of six months instead of a year or longer, though they varied across studies.
Those on the very low carbohydrate diets also experienced a greater increase in their HDL "good" cholesterol compared to those on the low fat diets.
However, participants on the very low carbohydrate diets also had greater increases in their LDL "bad" cholesterol levels than those on the low fat diets.
In blood pressure measurements, the participants did not differ on changes in their systolic blood pressure (top number).
Yet, those on the very low carbohydrate diets reduced their diastolic blood pressure (bottom number) more than those on the low fat diets did.
The researchers did not identify significant differences between participants of either diet in their measurements of blood sugar, insulin or other measures.
The authors concluded that individuals on very low carbohydrate diets lost more weight and reduced their diastolic blood pressure.
However, those on the very low carbohydrate diets also experienced increases in both their "good" and "bad" cholesterol levels.
"Hence, the very low carbohydrate ketogenic diet may be an alternative tool against obesity," the researchers wrote.
"Healthcare professionals should weigh the advantages and disadvantages of recommending a very low carbohydrate ketogenic diet and consider their patients’ will power, since this therapy prominently alters an individual’s daily habits," the researchers wrote.
Deborah Gordon, MD, a dailyRx expert who specializes in nutrition said this study "plants a solid if small win on the side of the low-carb weight loss advocates, starting with Dr. Atkins and continuing today through the work of Gary Taubes and many others."
She said she found the greater weight loss in the study impressive, even though it was small, as well as the increased HDL levels.
"HDL is reliably a marker of improved metabolic status, while LDL alone is less meaningful without knowing the size of the LDL particles," she said.
"For the many clinicians, including myself, who have seen far greater success with low carb diets than low fat, the meta-analysis is a welcome confirmation that will hopefully stimulate further individual studies that explore the degree and effect of carb restriction at different levels and in different settings," Dr. Gordon said.
The study was published in the June issue of the British Journal of Nutrition.
The research was funded by a grant from the National Council of Scientific and Technological Research and Development. The authors declared no conflicts of interest.