Reasonably good evidence suggests that most diets result in similar modest weight loss and improvements in cardiovascular risk factors over a period of six months, compared with a usual diet, finds a new study.
Weight reduction at the 12 month follow-up diminished, and improvements in cardiovascular risk factors largely disappeared, except in association with the Mediterranean diet, which saw a small but important 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 concern about the size of benefits.
To date, there has been no comprehensive analysis comparing the relative impact of different diets for 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 determine the relative effectiveness of dietary patterns and popular named diets among overweight or obese adults.
Their findings are based on the results of 121 randomized controlled trials with 21,942 patients (average age 49) who followed a popular diet or an alternative control diet and reported weight loss and changes in cardiovascular risk factors.
They grouped diets by macronutrient patterns (low carbohydrate, low fat, moderate carbohydrate, moderate fat, etc.) and according to 14 popular diet programs (Atkins, DASH, Mediterranean, etc.).
Most diets result in weight loss at six, but not 12 months
Compared with a usual diet, low carbohydrate and low fat diets resulted in a similar modest reduction in weight (between 4 and 5 kg) and reductions in blood pressure at six months. Moderate macronutrient diets resulted in slightly less weight loss and blood pressure reductions.
Among popular diets, Atkins, DASH, and Zone had the largest effect on weight loss (between 7.7 and 12 pounds) and blood pressure compared with a usual diet at six months.
No diets significantly improved levels of 'good' HDL cholesterol or C-reactive protein (a chemical associated with inflammation) at six months.
Overall, weight loss diminished at 12 months among all dietary patterns and popular diets, while the benefits for cardiovascular risk factors of all diets, except for the Mediterranean diet, essentially disappeared.
The researchers concluded that the evidence shows that most diets result in modest weight loss and substantial improvements in cardiovascular risk factors, particularly blood pressure, at six but not 12 months.
Differences between diets are, however, generally trivial to small, implying that for short-term cardiovascular benefit people can choose the diet they prefer from among many of the available diets without concern about the magnitude of benefits, they conclude.
Experts suggest that conversations should shift away from specific choice of diet, and focus instead on how best to maintain any weight loss achieved.
Source: BMJ, April 1, 2020.
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