While evidence suggests that most diets lead to similar modest losses in weight and improvements in cardiovascular risk factors such as blood pressure within 6 months, after 12 months, most of these improvements are lost.
To find this out, researchers analyzed the results of 121 randomized trials consisting of 21,942 patients (with an average age of 49) who followed popular named diets or alternative controlled diets who reported weight loss alongside changes in cardiovascular risk factors. To break down the data, they grouped the dieters according to their macronutrient patterns (low carbohydrate intake, low fat, moderate micronutrient) and according to 14 popular named diets such as Atkins, DASH (Dietary Approaches to Stop Hypertension) and Meditaranean.
In the end, the researchers noted that diets low in carbohydrates and fat resulted in modest weight reductions of 4-5kg and reductions in blood pressure within 6 months. Moderate macronutrient diets had similar, although slightly less significant results.
Meanwhile, among the popular named diets, the researchers found that Atkins, DASH and Zone had the largest effect on weight loss (3.5 kg- 5.5 kg) and reductions in blood pressure within six months when compared to more flexible diets. Noteworthy: none of the diets improved levels of HDL cholesterol or C reactive protein (a substance linked to inflammation) within the same time period.
At the 12-month mark however, the researcher noted that improvements in weight loss diminished among all diets studied, while cardiovascular risks similarly dissipated in all diets apart from the Meditarranean diet.
Although the researchers say that some limitations may have skewed their results, they believe that their data is still fairly accurate. Thus, they say with moderate certainty that most diets lead to modest, if any, overall improvements in weight loss and cardiovascular health. As positive results are nevertheless typically reached after 6 months of practically every diet studied however, they recommend people to choose a diet according to culinary preference.
However, rather than following it with absolution, they then recommend putting more attention on how to sustain positive results once gained. They said, “If we are to change the weight trajectory of whole populations, we may learn more from understanding how commercial diet companies engage and retain their customers, and translate that knowledge into more effective health promotion campaigns.”