Popular Atkins diet can heighten the risk of heart disease, say researchers.
Researchers from Sweden found that the introduction of the low-carbohydrate regime led to a surge in saturated fat intake in 2004, with an increase in cholesterol levels three years later.
"While low carbohydrate/high fat diets may help short-term weight loss, these results of this Swedish study demonstrate that long-term weight loss is not maintained and that this diet increases blood cholesterol, which has a major impact on risk of cardiovascular disease," the Daily Mail quoted study leader Professor Ingegerd Johansson, from the University of Umea, as saying.
In 2004 there was a sudden increase in the popularity of low carbohydrate/high fat (LCHF) diets like Atkins in Sweden.
The diets focus on cutting out sugar and starch while increasing intake of fats, including saturated fat.
Its proponents, such as Dr Annika Dahlqvist, who is credited with starting the Swedish craze, argue that it helps maintain normal weight and blood sugar while giving the people the freedom to eat their favourite foods.
A poll last year suggested that a quarter of Swedes had at least partly adopted an LCHF diet. Around five percent had taken it up seriously, leading the DietDoctor website to hail a "Swedish low carb revolution".
The latest study was launched in 1986 after concerns about the high incidence of heart disease in northern Sweden.
Scientists analysed data on food and nutrient intake, body weight, height and cholesterol levels compiled from more than 140,000 measurements and questionnaires between 1986 and 2010.
The results showed an initial reduction in fat consumption and cholesterol levels throughout the 1990s.
This coincided with the nationwide introduction of an education and food-labelling programme aimed at improving diet and health.
After 2004, there was an unexpected change. Levels of total and saturated fat intake began to increase until they were higher than they were in 1986.
Blood cholesterol levels remained roughly unchanged between 2002 and 2007, but then showed a steep rise.
In 2010 the average cholesterol level for men was around 5.5 millimoles per litre of blood, and for women it was slightly less. This was despite a significant increase in the number of people taking cholesterol-lowering drugs.
In earlier years, cholesterol levels had declined after reaching a high of more than six millimoles in 1986.
Over the whole 25-year period there was no sign that dieting of any kind helped people lose weight.
Average body mass index (BMI), a measurement relating weight and height, showed a consistent rise in weight in both men as well as women.
In their paper, the researchers said the marked increase in cholesterol levels after 2007 was 'a deep concern'.
"After 2004 fat intake increased, especially saturated fat and butter-based spread for bread and butter for cooking," the researchers said.
"Supportive opinions in media for high-fat diets seem to have had an impact on consumer behaviours. Initially beneficial and thereafter deleterious changes in blood cholesterol paralleled these trends in food selection, whereas a claimed weight reduction by high-fat diets was not seen in the most recent years.
"In contrast, BMI increased continuously over the 25-year period. These changes in risk factors may have important effects on primary and secondary prevention of CVD (cardiovascular disease)," they added.
The study was published in the Nutrition Journal.