Despite the addition of healthy foods such as salads and sprouts to the menu, fast food is less healthy today than it was 30 years ago, and is increasingly contributing to obesity, say researchers.
The study, led by Boston University, demonstrates that the calories, portion sizes, and sodium content overall have worsened (increased) over time and remain high.
"Given the popularity of fast food, our study highlights one of the changes in our food environment that is likely part of the reason for the increase in obesity and related chronic conditions over the past several decades, which are now among the main causes of death," said lead investigator Megan A. McCrory, from the varsity.
"Our study offers some insights on how fast food may be helping to fuel the continuing problem of obesity and related chronic conditions," McCrory added.
For the study, published in the Journal of the Academy of Nutrition and Dietetics, the team examined changes offered by 10 of the top fast-food restaurants over the 30-year period from 1986 to 2016.
They found that the total number of starters, desserts and side dishes increased by 226 per cent, or 22.9 items per year.
Calories in all three categories increased significantly, with the largest increases in desserts (62 kcals per decade), followed by starters (30 kcals per decade).
These increases were mainly due to the increase in portion size, which was statistically significant in entrees (13 grams per decade) and desserts (24 grams per decade) categories.
Sodium also increased significantly in all menu categories, while iron levels increased significantly in desserts.
Changes in calcium and iron levels, particularly in desserts, is a positive development since these nutrients are important for good bone mass and preventing anaemia.
There are, however, better sources (foods) that do not come with high calories and sodium, the researchers said.
"We need to find better ways to help people consume fewer calories and sodium at fast food restaurants. The requirement that chain restaurants display calories on their menus is a start," McCrory said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)