Two decades after the debate began on which diet is best for weight loss,a conclusion is starting to come into focus. And the winner is not low-carb,not low-fat,not high protein,but any diet. That is,any diet that is low in calories and saturated fats and high in whole grains,fruits and vegetables and that an individual can stick with is a reasonable choice for people who need to lose weight.
Thats the conclusion of a study published recently in the New England Journal of Medicine,representing the longest,largest and most rigorous test of several popular diet strategies.
In the light of another highly regarded study published last year that reached a similar conclusion,medical experts are embracing the back-to-basics idea that the simple act of cutting calories is most important when it comes to losing weight.
The conclusions could end the often-contentious debate over the comparative effectiveness of diets that are predominantly low in fat,high in protein,low in carbohydrates or marked by other specific configurations of nutrients. This study is saying it doesnt make any difference what diet you choose. Calories have always been the bottomline, said Dr Robert Eckel,a physiology professor at the University of Colorado Health Sciences Center and past president of the American Heart Association. The findings should free people from the notion that its necessary to eat a specific ratio of fat,protein and carbohydrates. They should choose what works for them.
There isnt any one way. That is the nice thing about none of these diets in particular winning, said Christopher Gardner,a nutrition researcher at Stanford Universitys Prevention Research Center. We dont have any right to push low-fat or low-carb or high-protein. If one of these approaches is more satiating,where you will not be hungry or have cravings,that is the one that will work for you.
The study did not prove,however,that every dieter succeeds. Instead,it reinforces numerous other studies,showing that most people lose a modest amount of weight in the first few months of dieting and regain some or all of it over time.
In the current study,the average weight loss was 13 pounds at six months and 9 pounds at two years. The research followed 811 overweight or obese people,62 per cent of whom were women,enrolled at one of two sites: Harvard School of Public Health in Boston or the Pennington Biomedical Research Center of Louisiana State University in Baton Rouge.
The participants were assigned to one of four diets: low-fat,average-protein; low-fat,high-protein; high-fat,average-protein; and high-fat,high-protein. The diets ranged from 1,200 to 2,400 calories per day based on each individuals body mass index and gender,but everyone was asked to cut about 750 calories a day from what they normally ate.
All the diets were low in saturated fat,the kind linked to heart disease and found in many fried or processed foods. Participants were asked to do 90 minutes a week of moderate exercise. They kept a food diary,and a web-based programme provided feedback on how closely they met their goals. Individual and group counseling sessions were held over the two years. We were trying to focus on just those three nutrients fat,protein and carbohydrates and keep everything else,like saturated fat and fiber,as consistent as possible, said Catherine M Loria,project scientist at the National Heart,Lung and Blood Institute,which funded the research.
This shows people can just focus on counting calories. They have a lot of flexibility. Its a great finding. The study refutes the notion that any one nutrient has a special power to accelerate weight loss,said Dr Frank M Sacks,lead author of the study and a professor of cardiovascular disease prevention at Harvard University.
We used to think there could be a biological effect of certain diets. That is probably not true. There might be a strong behavioral effect in the success of a diet,however. The people who attended two-thirds or more of the counseling sessions over the two years lost an average of 22 pounds compared with the average loss of nine pounds.
The study was highly anticipated because diet research over the past two decades has come to dramatically different conclusions.
Some studies showed a very low-fat,strict vegetarian diet was best, Sacks said. Others had Atkins diets doing better. So the question we had was,how do we reconcile all that? Many of the previous studies were held over six months or less,enrolled small numbers of people (usually women) and sometimes involved feeding participants prepared meals instead of allowing them to follow the diet on their own in real-life conditions,Gardner said. Some studies also attracted media attention and marketing hype that might have contributed to the success of regimens,Sacks said. In this study we wanted to neutralise these diets, he said. No marketing. No expectations. All the diets were healthy. We told the participants that experts are completely at odds about which would be better.
Another study,published in July in the New England Journal of Medicine,found the Atkins and Mediterranean diets were somewhat more effective than a low-fat diet. But that studys authors also recommended choosing a diet according to individual preferences. Few of the people in the current study strictly adhered to the calorie limits and the composition of their diets,suggesting it is just too difficult to do so,Garner said.
For example,those assigned to consume 35 per cent of their calories as carbohydrates actually consumed an average of 43 per cent,and groups that were supposed to eat a 20 per cent-fat diet averaged 26 per cent. In the end,many of the participants were eating diets that were more similar than dissimilar.
If the diets are blurring together,then one might expect that the results would be similar, Gardner said. In reality,trying to follow a low-fat or high-protein diet really has a negative impact on adherence.