In the search for the solution to the growing waistlines of Australians, many popular diets have been tried and eventually discarded. There are literally hundreds of dieting books and programs to choose from, with many popular ones substantially departing from mainstream nutrition and medical advice.
So should it be low-fat, low-carbohydrate, high-protein, low-glycaemic index, small meals or any one of a myriad of other popular dieting approaches? The scientific jury is now firmly in with dozens of high-quality randomised controlled trials showing that no one dieting option is the magic solution for everyone.
State of the evidence
Apart from some short-term success for particular approaches, mostly low-carbohydrate diets, all of the popular dieting approaches fare poorly in terms of weight loss, weight maintenance and adherence once the 6-month milestone is passed.
To illustrate the current state of evidence, one of the largest and longest randomised-controlled trials  ever conducted considered how diets with different fat, protein and carbohydrate content can influence weight loss.
Over 800 overweight adults took part in the study. Each person was randomly allocated to one of four diets each consisting of similar foods and was designed to meet guidelines for cardiovascular health. Diets were either low or high in fat (20 or 40% energy from fat) while the carbohydrate content varied (35, 45, 55 or 65% of total energy) with protein making up the remainder of the diet. Each person was offered group and individual instruction and support sessions over the two years the study ran.
After 6 months, average weight loss was 7% of initial body weight with negligible differences between the different diets. Predictably, much of this weight loss was regained with only half of it maintained by two years. All the diets improved blood lipids and insulin levels. Rare for a weight loss study of this length, 80% of participants completed the study.
One kernel of positive news from the study was that those people who lost more weight attended more counselling sessions and likewise adhered more closely to their prescribed diet plan. This finding is not alone in the scientific literature as ongoing support, no matter what the diet program, has been shown to be an essential part of helping to achieve weight-loss success.
If people find it difficult to stick to a diet, despite expert advice and ongoing follow-up and support as used in this research study, then the chances of success in the ‘real-world’ is even more remote. The rising rates of obesity in the face of continual best-selling ‘breakthrough’ diet plans attest to that.
Some diets better than others
With differences between many of the popular dieting options marginal at best, that does not mean that they are all to be equally recommended.
Recently, a panel of 22 nationally recognised experts in diet, nutrition, obesity, food psychology, diabetes, and heart disease reviewed 25 different diet plans. Read about the full analysis of the diets here .
Each diet underwent intense scrutiny, with no fewer than 19 experts rating any individual plan. Ratings were given based on: how easy the diet is to follow, its ability to produce short-term and long-term weight loss, its nutritional completeness, its safety, and its potential for preventing and managing diabetes and heart disease.
The best diet overall went to the Dietary Approaches to Stop Hypertension (DASH) diet which is based on an eating plan high in fruits and vegetables, low-fat dairy, and plenty of whole grains. In second place overall was the Therapeutic Lifestyle Changes (TLC) diet, which is high in fibre and low in fat. The TLC diet was developed by the National Institutes of Health National Cholesterol Education Program and is endorsed by the American Heart Association. Third place was a tie between Weight Watchers, the Mayo Clinic diet, and the Mediterranean diet.
Rounding out the bottom of the list with the poorest overall rankings were the popular fads of the Atkins’ diet, raw food diet, Dukan diet and in last place, the palaeolithic diet.
Habits of successful 'weight losers'
Long term, almost any rigid dieting approach is destined to fail. Yet we can learn much about 'what works' from observing the nutrition and lifestyle habits of people who are successful at taking weight off, and importantly keeping it off. The US National Weight Control Registry  is one such source. The Registry collects details of individuals who have successfully lost more than 13 kg for a year or more and analyses their weight loss strategies. To date over 2,500 people have made it on the registry since it was first established in 1994.
People on the registry on the whole got there not by following a special diet, but instead by adopting realistic and sensible long-term lifestyle changes. They mostly eat foods that are high in carbohydrate and fibre and low in fat, eat breakfast each day (which reduces the chance of overeating later in the day), weigh themselves at least once per week and most importantly – become more physically activity.
Forget about conservative National Physical Activity Guidelines for Adults  to exercise for at least 30 minutes per day on most days of the week, data from the registry and supported by several intervention studies shows that at least 1 hour per day of physical activity (walking being the most popular) is needed to have a realistic chance of losing and keeping weight off.
Adding to the Registry data, a comprehensive review  of the scientific literature has specifically looked at common themes and strategies that predict weight maintenance and a summary of these is listed following.
- Having regular and ongoing support be it through a community based weight loss group, a dietitian or GP, on the internet, or through friends
- Using behaviour change techniques such as goal setting, self-monitoring of weight, relapse prevention and of course sensible diet and physical activity changes
- Becoming (and staying) more active alongside a moderately energy reduced diet of around 2500 kJ (600 Calories) per day.
- Eating less fat (which is high in kilojoules) and more protein (which may help reduce appetite and preserve muscle mass)
What it all means for you
Dieting is not the way to achieve long-term weight loss. The key to long-term success lies in learning from those people who are successful in losing and keeping weight off. Small and realistic lifestyle changes appear to be the best recipe combined with ongoing support and advice.
Confused about the mixed soup of nutrition messages being stirred through the media? Tim maintains an active nutrition blog at www.thinkingnutrition.com.au  where you'll find the latest nutrition research and controversies discussed in straight forward language, distilling out what you need to know for your better health.