Although the majority of Australians are overweight or obese by the time they're middle-aged, an enviable minority stay slim. Are they just genetically gifted or do they have to work at keeping their weight down?

To try to find the answer to this weighty question, Consumer Reports, CHOICE's US counterpart, asked a total of 21,632 subscribers in 2007 about their lifetime weight history and their eating, dieting and exercising habits.

The study found that there are six strategies that correlate most strongly with a healthy body mass index (BMI) – and any of us can follow them.

Breaking it down

Those responding to the survey were separated into three main categories: 

  • Always-slim – people who've never been overweight (16% of the sample). 
  • Successful losers – people who, at the time of the survey, weighed at least 10% less than they did at their heaviest, and have kept the weight off for at least three years (15% of the sample). 
  • Failed dieters – people who said they'd like to slim down, yet still weighed in at or near their lifetime high (42% of the sample). 

The remaining 27% of respondents (such as people who'd lost weight more recently) didn't fit into any of these categories.

The responses and feedback from this survey are every bit as relevant to Australian consumers as to those in the US. Of all respondents, 66% were overweight as assessed by their BMI (similar to the US population as a whole). One-third of this group, or 22% of the overall sample, qualified as obese. Australia has similar levels, with combined overweight and obesity incidences of about 60%, and 20.8% of all adults qualifying as obese.

Diets that work

People who've never been overweight aren't sitting in a recliner with a bowl of chips on their laps. In the group of always-slim respondents, just three per cent said they never exercised and ate whatever they pleased. "Naturally slim" people aren't just winners of the genetic lottery; their eating and exercise habits are very similar to those of people who've successfully lost and kept off weight. Both groups:

  • eat healthy foods such as fruits, vegetables and wholegrains
  • deliberately avoid excessive dietary fat
  • practice portion control
  • exercise vigorously and regularly.

The only advantage the always-slim have over the successful dieters is that these habits seem to come a little more naturally.

"When we compare people maintaining weight loss with those who've always been a healthy weight, we find that both groups are working hard at it; the maintainers are just working a little harder," says Suzanne Phelan, PhD, co-investigator of the US National Weight Control Registry, which tracks people who've successfully maintained their weight loss.

Successfully losing weight means exercising a little more and eating with a bit more restraint than an always-slim person, as well as using monitoring strategies such as weighing themselves regularly or keeping a food diary.

Six strategies to keep the weight off

There are six key behaviours that correlate most strongly with being and staying slim or having a healthy BMI that came out of the Consumer Reports study. By following these strategies, you too can control your own weight.

  1. Watch portions. Of all the eating behaviours, carefully controlling portion size at each meal correlated most strongly with having a lower BMI. Of those who had successfully lost weight, 62% reported practicing portion control at least five days per week, as did 57% of the always-slim. However, only 42% of failed dieters practised portion control.
  2. Limit fat. This means restricting fat to less than one-third of your daily kilojoule intake. Fifty-three per cent of successful losers and 47% of the always-slim said they did this five or more days a week, compared with just 35% of failed dieters.
  3. Eat fruits and vegetables. The more days that respondents ate five or more servings of fruits or vegetables, the lower their average BMI. In both the successful losers and the always-slim groups, 49% said they ate that way at least five days a week, while just 38% of failed dieters did so.
  4. Choose wholegrains over refined. People with lower body weights opted for wholegrain breads, cereals and other grains over refined (white) grains more frequently than failed dieters.
  5. Eat at home. As the number of days per week respondents ate restaurant or takeaway meals for dinner increased, so did their weight. Eating at home saves money too.
  6. Regular vigorous exercise. The type of exercise that increases heart rate for 30 minutes or longer was strongly linked to a lower BMI. Although only about one-quarter of respondents said they did strength training at least once a week, the practice was significantly more prevalent among successful losers (32%) and always-slim respondents (31%) than it was among failed dieters (23%).

Many of these healthy lifestyle strategies are highlighted in the Dietary Guidelines for Australian Adults, developed by the government's National Health and Medical Research Council (NHMRC).

General diet tips

Embracing some or all of these strategies may increase your weight-loss success. In addition, consider these tips:

  • Don't get discouraged. Studies show that prospective dieters often have unrealistic ideas about how much weight they can lose. A 10% loss might not sound like much, but it can significantly improve overall health and reduce the risk of disease.
  • Ask for support from friends and family to help you stay on track – by not pestering you to eat foods you're trying to avoid, or not eating those foods in front of you.
  • Get up and move. Although regular, vigorous exercise correlated most strongly with healthy body weight, the findings suggest any physical activity is helpful, including activities you might not even consider exercise. Housework, gardening and playing with the kids were modestly tied to lower weight. Hours spent sitting each day – at an office desk or at home watching TV – correlated with higher weight. The latest physical activity guidelines suggest around 60 minutes of exercise, five days a week.

Weight loss strategies that make little difference

  • Lowering your carbohydrate intake. In its survey, Consumer Reports found that limiting carbohydrates was actually linked to higher BMIs. Although this doesn't necessarily mean low-carb plans such as the Atkins or South Beach diets don't work, the findings suggest that cutting carbs alone, without exercise or portion control, may not yield great results.
  • Eating many small meals.
  • Not eating between meals.
  • Including lean protein with most meals.

Are you overweight?

To calculate your BMI (body mass index), divide your weight (in kilograms) by your height (in metres), squared.

  • Underweight: BMI <18.5
  • Healthy weight: BMI 18.5 to 24.9
  • Overweight: BMI 25 to 29
  • Obese: BMI 30+

15 tips for healthy eating on a budget

Healthy foods such as fruits and vegetables can be more expensive (serve for serve) than potato chips and chocolate bars. But that doesn't mean you should resign yourself to getting fat if you're on a budget. These simple tips can help you stretch your budget without stretching your waistline:

  1. Buy in season. This improves your chances of getting the freshest produce, and you avoid paying for shipping. See our list of fruit in season.
  2. Try supermarket generics. Quality doesn't always come at a price premium. Some supermarket brands – particularly home-brand staples such as sugar, salt and flour – are often just as good as pricier name brands.
  3. Buy frozen produce. Frozen fruits and vegetables – often frozen soon after picking – can be more nutritious than "fresh" items from your local supermarket, which may have sat on store shelves for a while. By using the frozen variety, you don't have to worry about it spoiling before it's eaten – fruit and veggies make up the bulk of food wasted by Australians every year.
  4. Eat pulses such as beans, chickpeas and lentils. They're inexpensive, versatile and a great source of protein and fibre. Add them to salads, soups, stews and pasta dishes to increase bulk. Canned pulses are the most convenient – but, for maximum economy, buy dried.
  5. Mix a big fruit salad. Squeeze lemon juice over it to stop it going brown, then divide it into individual food-storage containers for breakfast, dessert or a snack each day. Making your own costs much less than buying deli- or store-made fruit salad. Be careful of the number of fruit serves if you're dieting, though.
  6. Bake a potato. With the right additions, it can make a satisfying meal. Add healthy or creative toppings such as cottage cheese, plain yoghurt, beans, low-fat cheese or salsa. Sweet potatoes can offer even more nutrients.
  7. Avoid packaged drinks. Dilute juice to cut down on kilojoules as well as cost. Don't buy bottled water – drink tap instead. Invest in a reusable polyethylene (opaque plastic) water bottle to store it.
  8. Buy in bulk. Buy extra chicken, meat or fish when they're on special and freeze what you don't eat straight away. Buy large packages of snacks and re-bag. Buy fruit and veg with a longer shelf life (such as apples, oranges, potatoes and onions) in the large pre-packaged bags rather than a few at a time – but use unit pricing to compare value, as buying in bulk isn't always the cheapest option.
  9. Buy a whole chicken. It's more economical than buying separate breasts, thighs and wings, and you can get a nutrient-packed stock out of it, too. Freeze the pieces you don't use in individual freezer bags.
  10. Put meat and poultry on the side. Keep meat and poultry to the recommended serving size of 65–100g. Fill up your plate with wholegrains and in-season or frozen vegetables.
  11. Use your scraps. Cook leftover meat and vegetables into a frittata, quiche or omelette; eggs are a great source of protein. Use bones, meat or vegetable scraps to make stock. 
  12. Grow your own veggies. This requires a little time, but can have nice payoffs (including exercise).
  13. Know your supermarket. Products that make the largest profit margin are usually at eye level in supermarket aisles, so check higher and lower shelves for better bargains. For more tips, see supermarket sales tricks.
  14. Plan ahead. To help avoid impulse buying, make a weekly menu and shopping list and get everything you need in one trip.
  15. Cook for the week. One-pot meals such as casseroles, pot-roasts, soups and stews use cheaper cuts of meat, and you can divide into portions and take to work for lunch or freeze the remainder for later. Slow cookers are great for one pot meals.