Slimmers turning to low-fat foods could be piling on the pounds.
Nutritionists warn that while most people are aware fruit juice, breakfast cereals and salad dressings can contain large amounts of sugar, many are less conscious of sugar levels in low-fat foods.
"Eliminating sugar from your diet completely is almost impossible because sugar is hidden in everything,'' Tauranga-based medical herbalist and clinical nutritionist Angela Frieswyk said.
"One thing people commonly forget about is yoghurt. In a standard pot of yoghurt there are 25 to 27g of sugar and a teaspoon of sugar is 5g so that's about five to six teaspoons of sugar in one serve.''
She advised clients to check food labels and not eat anything that had sugar in its first four ingredients. And keep in mind sugar can be disguised by different names, such as sucrose, corn syrup, fructose and glucose.
"Sugar is an empty calorie and it doesn't provide nutrition to sustain you for long.
"Foods with low GI (glycemic index) are slow release energy and will not immediately lift you up but are more sustaining and make you feel more alert for longer, a lot fuller for longer and ultimately more satisfied,'' she said.
Tauranga registered dietitian Fiona Boyle, of Food Solutions, said it was important to distinguish between natural and refined sugars and limit the latter.
When too much sugar was consumed, it was added as extra calories and could lead to weight gain and increased blood sugar.
And when high amounts of sugar were consumed regularly, people could become addicted to the high, Ms Boyle said.
"That's when things can get out of balance - when they choose sweet options at the expense of other foods.''
Dentist Alastair Miller, from The Dentists in Otumoetai, said sugary food, particularly fizzy drinks, were causing increasing incidence of tooth decay.
Energy drinks were particularly bad as they had a high acid content which stripped teeth of protective enamel.
However, registered dietician Rachel Scrivin, of FoodFX, said sugar was still an important part of a healthy, balanced diet.
Endurance athletes needed sugar to give them an energy hit while the average person did not need the same amount of sugar, and if they did consume more than they needed, it would be stored as extra calories.
Some people tried to make good choices but the foods they thought were healthy were not. Foods that caught people out included sushi (high in sugar and salt), fruit drinks, smoothies, sports drinks and processed breakfast cereals.