New research shows people with diabetes looking to lower their weight don't need to count protein or carbs to get the best effect.
Otago University researchers have found the best way to shed kilos is to simply lower overall intake, rather than focus on carbohydrates or protein.
While slightly effective in the short term, these diets balance out in the long term - leaving no difference compared to other diets, and little change overall.
In a study headed by Dr Jeremy Krebs and funded by the Health Research Council, 419 overweight and obese people with diabetes aged 35 to 75 were put on two different low fat diets: one involving a high protein intake and the other with a high carbohydrate intake.
The study lasted two years, and the results were clear cut: there was little difference between the two diets.
The participants did lose weight, but not for the reasons that might be expected. The weight loss was directly linked back to the reduction of total calorie intake - or, rather, the participants eating less.
The head of the study, Dr Jeremy Krebs from Otago University in Wellington, said it showed that dieting is, simply, difficult.
"There's no easy route," he said.
"We certainly did achieve a modest weight loss, of two to three kilos, in both groups, but essentially there was little difference between the two diets.
"This confirms that the solution to weight loss over the long term is reducing energy intake; that is the amount of calories someone eats on a daily basis."
The study also had a 30 per cent drop-out rate, which Dr Krebs said was considerably higher than the standard 20 per cent rate the researchers were anticipating.
"Even those who stuck to the diet, more or less, did not reach the level of protein or carb intake recommended by the study over the two-year period.
"Often people drift back to their old eating habits and the behaviour of many participants in this study also illustrated this tendency.
The real key to obesity in people with type 2 diabetes, and to better blood sugar control, is to focus on cutting calorie intake over the long term."
Dr Krebs stressed that dieting is a strictly personal endeavour - different diets work for different people, and no one diet can function as a cover all.
"People find it hard to stick to any diet - and so we stress that whatever particular diet approach suits a person, they should follow it," he said.
Jim Mann, professor in Human Nutrition and Medicine at the University of Otago as well as the director of the Edgar National Centre for Diabetes and Obesity Research and the WHO Collaborating Centre for Human Nutrition, said the study was an example of common sense.
"It may not sound profound, and that's because it's not, really," he said.
"But it's really quite an important paper. There is a huge battle at the moment between proponents of the different kinds of diets - high carbohydrate, high protein and so on - but what the study shows is the important thing is for people cut calories, and not obsess about carbs and fat."
"It's putting it out there so people actually get the message."
Food industry nutritionist at the Heart Foundation, Judith Morley-John, agreed, saying that exercising, and eating quality food, was also important.
"It's a great study," she said.
"It's often the quality of the food as well - vegetables, fruits, wholegrains, lean meat and the like.
"Physical activity is really important to weight loss as well," she added.
"Of course, prevention is better in the first place."