Fruit and vegetables are always a safe bet.
Low-fat diet is best for weight loss
The most famous fall guy for the obesity epidemic is dietary fat and we are still living with the legacy of the ''low-fat'' mantra. Just look at the abundance of ''low-fat'' and ''light'' foods in supermarkets.
Weight loss is the result of eating fewer kilojoules and exercising more. The trick is to maintain a high nutrient intake in fewer kilojoules - this is where food choice is paramount.
Choosing the most nutrient-dense foods from all food groups will ensure you stay well-nourished at the same time as burning body fat. A fat-free diet does not contain enough essential fatty acids and fat-soluble vitamins, and leaves a massive flavour black hole.
A Cochrane Review (the ant's pants of scientific studies) of research concluded low-fat diets had no advantage over kilojoule-restricted diets for weight loss. You can still lose weight eating healthy fats, as long as your diet is kilojoule-controlled. A healthy diet contains about 30 per cent of kilojoules as fat.
Foods low in fat are not necessarily low in kilojoules. Those with a low moisture content, such as ''baked not fried'' or ''light'' biscuits, crackers and crisps, are great examples of foods that are still high in kilojoules despite being made to a lower fat recipe.
There is a place for low-fat foods - in the dairy aisle. Because dairy is a major source of artery-clogging saturated fat, low-fat versions of these nutrient-rich foods are recommended for everyone aged over two.
Nuts are fattening
This is one of those ''too much of a good thing'' stories. Nuts (along with seeds) are nutrition powerhouses packed with protein, vitamins, fibre, good fats and essential minerals. They also have lots of kilojoules thanks to a high (good) unsaturated fat content.
We need some nuts. To keep your heart healthy, it is a good idea to tuck into a handful or two (depending on your energy needs) of unsalted nuts each day or have some nut butter on your toast. Or add nuts to your cooking.
Portion caution is the issue with nuts - they are so moreish many people find it hard to stop.
Butter is better than margarine
I've done some consulting work for a company that makes margarine, so I have some inside information on this one. I've had long chats with food technologists whose job it is to tweak the recipe, and talked to top-notch scientists to sort through the evidence.
I eat margarine myself and recommend it over butter to my family and friends.
Margarine is made from vegetable oils, with just enough hard fat (often palm oil) to make it spreadable. It has vitamins A and D added (required by law), an emulsifier (often lecithin from soybeans) to stop it separating, a little salt for taste, natural colour and a preservative to keep it fresh.
Sometimes a little milk is added, also for taste. About 99 per cent of the ingredients in a typical margarine spread are from natural sources (the preservative is not). Margarine is not much more processed than butter.
To be fair, margarines developed a bad reputation because of the presence of trans-fats.
These bad fats are produced when liquid oils are partially hydrogenated to make them solid at room temperature. However, when the science emerged that these were harmful, reputable manufacturers changed the way they made table margarine.
There may be a few cheap variants that still contain some trans-fat - check the label before buying.
Butter is made from cream and is almost 70 per cent saturated fats that increase cholesterol. Every tablespoon of butter is eating the equivalent of two tablespoons of pure cream- not milk - which is why it isn't part of the dairy food group.
Eating butter and cream will increase your blood cholesterol and they don't give you any calcium.
Butter is 80 per cent fat but contains no essential fats (omega-6 and omega-3). Although it does contain some vitamin A, so does margarine. It's a real ''sometimes food'' - all about taste and nothing about health.
Sea salt is healthier
Sea salt oozes natural food cred, with exotic and expensive, coloured single-origin salt revered by chefs and gourmands. The fact is, although sea salt (or any other fancy kind of salt) may add subtle differences in flavour and texture, it contains just as much harmful sodium as regular ''el cheapo'' table salt. In terms of mineral content, the amounts are so small you would need to poison yourself with sodium to obtain useful quantities of minerals that are otherwise found in nutritious foods.
Eggs increase cholesterol
Ever wondered why egg-white omelettes became so popular? Heaven knows, it wasn't for the flavour. Eggs were shunned because of their cholesterol content. But looking a little deeper, we find eating eggs is not linked with higher rates of heart disease. Although eggs contain cholesterol, eating eggs in moderation as part of a heart-friendly diet low in saturated fat will not adversely affect the blood-cholesterol level of most people.
Blood-cholesterol levels are far more influenced by how much saturated and trans-fat you eat than dietary cholesterol.
Frozen foods are less nutritious than fresh
The usual suspect for this popular myth is vegetables. And it's probably true: nothing will be more nutritious and tasty than vegetables freshly picked from the garden and served the same day.
These days, frozen vegetables come close. They are picked at their peak and snap-frozen within hours, which makes them a nutritious option. In fact, frozen peas will retain more of their vitamins and minerals than the shelled pre-packed peas on the greengrocer's shelf.
Low-carb beer is healthier
Low-carb beer is a classic case of wishful thinking, or perhaps an example of ignoring the elephant in the room. Yet low-carb beers are still a hit. How could so many people have been hoodwinked into thinking a beer with fewer carbs is healthier when it's the alcohol content that's the problem.
The first, rather obvious, thing to point out is beer contains low levels of carbohydrates. The average lager-style beer contains only 2 per cent carbohydrate (sugars) by volume, or 7.5 grams in a 375-millilitre can. As a point of comparison, soft drinks contain 40 grams (eight teaspoons) of sugar in every 375-millilitre can. You should know carbohydrates are not especially fattening, although sugars in drinks are not nutritious.
The real nail in the coffin of logic behind the marketing of low-carb beers is that they contain the same level of alcohol as regular beers, and the alcohol is the kilojoule (calorie) culprit, contributing 75 per cent of the total.
If you really want to curb the kilojoules, then drinking low-alcohol or ''light'' beer makes more sense. Or, better still, less beer.
Nicole Senior is an accredited practising dietitian and nutritionist. This is an edited extract from her book Food Myths, published by New Holland ($16.95).