"People think food for general healthy eating is the same as food for weight loss, and it's not."
With more than 65 per cent of New Zealanders overweight or obese, the messages need to change, she says.
Breakfast
People trying to lose weight may be doing themselves a disservice by starting the day with breakfast cereal. Because cereal is a carbohydrate, it does not give lasting energy, Spence says, prompting snacking later, particularly for people with a high muscle mass who process carbohydrates quickly. Toasted muesli is high in sugar and oils and loaded with kilojoules.
Most cereals are promoted in a way that makes people think they are the perfect food, she says.
"They can be high in fibre and low in fat, but do they keep you feeling full for long enough?"
Spence recommends adding protein, such as baked beans or eggs, to the first meal of the day. "You will get much better appetite satisfaction if you include protein."
And everyone should eat breakfast. "If you wake up and you are not hungry, you have eaten too much from 4pm the day before."
Water
Most people should drink 1.5 litres of water a day minimum during summer and a litre during winter, Spence says. "But over-drinking won't do you any good. It just results in additional trips to the toilet, and possibly a loss of water-soluble vitamins."
AUT University Professor Elaine Rush agrees there is evidence of people drinking too much water. "Advertising does work. There are all the myths that go with bottled water." Rush says people can gauge whether they're drinking enough fluid by the colour of their urine.
Carbohydrates and protein
Restricting carbohydrates in meals is not sustainable, Spence says. "There are people who never have potato at night but you find the meat portion just gets a bit bigger, and that actually contains more calories."
Anyone who drops carbohydrates from two meals a day will notice they are tired by the end of a week on the diet, she says. "It doesn't meet enough needs nutritionally."
While eating more protein is good, Spence says recent studies show a small increase in the amount of protein noticeably reduces the number of calories eaten overall, but too much protein quickly leads to weight gain.
A good rule is to eat half a plate of vegetables, a quarter of carbohydrates and a quarter of protein, says Rush. Protein shakes and meal replacements also get the thumbs down. "There's a strong relationship between chewing your food and increased appetite satisfaction," Spence says.
Rush says eating plans should be about quality of life. "It doesn't matter how good the quality of the petrol you put in the tank is, it's getting it away from the kerb that matters. You need to be able to function."
The gym
Slogging away for hours at the gym is unlikely to make a lot of difference to weight-loss efforts, Spence says.
"You can do a lot of exercise, but unless you get the food right, nothing will happen." Once people are carrying extra body fat, exercise is not as effective as many think. Ideally, people should go for a brisk walk for 30 minutes a day.
"Any longer than 35 minutes a day may just make you hungry."
Dr Geraldine Poynter, who refers clients to Spence, says people find the idea of a half-hour walk more palatable. "A short, brisk walk is so achievable."
Good fats
In terms of weight loss, it doesn't matter if they are "good" or "bad" fats - it's all bad if you eat too much.
Says Spence: "When you look at fresh salmon, seeds, avocado, overweight people think this is good for them but they are loaded with calories." Poynter says the information she learned from Spence was a surprise.
"I thought we were meant to have a lot of Omega-3, so I was eating salmon. She says it is better to eat canned salmon because it is not so fatty. At medical school we got so little nutrition information."
Low GI
The glycaemic index has been a buzzword in weight loss in recent years, as it indicates how long it takes food to be broken down and start affecting blood sugar levels.
But Spence warns that people should not think that a low-GI diet, said to make you feel full longer, is a fast track to weight loss.
"There is certainly no harm in choosing low-glycaemic index foods. However, they are not a strong factor in successful weight loss."
People still need to ensure they eat appropriate portion sizes. While low-GI food might give a more sustained release of energy throughout the day, it can be calorie-dense.
Rush says: "Usually things with low GI are good for you because they contain things such as fibre, but it depends on the combination they are eaten in."
One size does not fit all
People who are serious about weight loss should find out exactly how much body fat and muscle mass they are carrying. "Find out the truth about who you are feeding." Spence uses a high-tech machine to assess muscle and fat mass, and metabolic rate to assess dietary needs. Versions of the machine are available at chemists.
No two bodies are the same - even two men of the same height and weight can be different, she says. Put an All Black and an overweight man on the same diet and one will lose weight and the other will gain.
