Some pretty good evidence suggests that most diets over a six-month period lead to comparably modest weight loss and improvements in cardiovascular risk factors, compared to a regular diet, according to a new study.
Weight reduction at the 12-month follow-up declined and improvements in cardiovascular risk factors largely disappeared, except when combined with the Mediterranean diet, which saw a small but significant reduction in "bad" LDL cholesterol. As such, at least for short-term benefits, the researchers suggest that people should choose the diet they prefer without worrying about the magnitude of the benefits.
Obesity has nearly tripled globally since 1975, but until now there has been no comprehensive analysis comparing the relative impact of different diets on weight loss and improving cardiovascular risk factors, such as blood pressure and cholesterol levels.
To address this, a team of international researchers set out to investigate the relative effectiveness of dietary patterns and popularly named diets in overweight or obese adults.
Their findings are based on the results of 121 randomized trials involving 21,942 patients (mean age 49) who followed a popularly termed diet or an alternative control diet and reported weight loss and changes in cardiovascular risk factors. The studies were set up differently and of varying quality, but the researchers were able to include that in their analysis.
They grouped diets based on macronutrient patterns (low-carb, low-fat, and moderate macronutrient - similar to low-fat, but slightly more fat and slightly less carbohydrates) and according to 14 popular diet programs (Atkins, DASH, Mediteranean, etc.).
Compared to a regular diet, low-carb and low-fat diets resulted in a similar modest weight reduction (between 4 and 5 kg) and a reduction in blood pressure after six months. Moderate macronutrient diets resulted in slightly less weight loss and blood pressure reductions.
Of the popular diets, Atkins, DASH and Zone had the greatest effect on weight loss (between 3.5 and 5.5 kg) and blood pressure compared to a normal diet at six months. None of the foods significantly improved levels of "good" HDL cholesterol or C-reactive protein (a compound associated with inflammation) after six months.
Overall, weight loss decreased at 12 months on all diets and popular named diets, while the cardiovascular risk factor benefits of all diets except the Mediterranean diet essentially disappeared.
The researchers point to some study limitations that could have affected the accuracy of their estimates. But say their extensive search and in-depth analyzes support the robustness of the results.
As such, they say moderate certainty shows that most macronutrient diets result in modest weight loss and substantial improvements in cardiovascular risk factors, especially blood pressure, at six but not 12 months.
However, differences between diets are generally trivial to minor, meaning that for short-term cardiovascular benefits, people can choose the diet they prefer from many of the available diets without worrying about the magnitude of the benefits, they conclude.
The vast array of popular diets analyzed "offers plenty of choice, but no clear winner," researchers from Monash University, Australia, say in a linked editorial.
As such, they suggest that conversations should move away from a specific diet choice and focus on how best to maintain weight loss.
Since dietary guidelines are not popular with the public, it is good advice for individuals to take a food-based approach and encourage them to eat more vegetables, legumes and whole grains and less sugar, salt and alcohol. /P>
