As expected, yogurt desserts ranked the highest, containing 16.4g of sugar per 100g on average.
The NHS recommends that adults not exceed 30 grams of free sugar - defined as sugar added to or naturally found in foods - each day, while parents are encouraged not to give children under 4 foods with added sugar.
The fat content of yogurt is less of a worry than sugar as most products would not contribute a high proportion to the recommended daily intake of fat (on average, 97g for a man and 78g for a woman).
So unless it's using artificial sweeteners, if your yogurt tastes sweet, it's probably because there's sugar in it. The authors of the study calculated the median amount of sugar per 100 grams for each category of yogurt that they studied, and compared sugar averages.
This is "concerning" given the rise in childhood obesity and the prevalence of tooth decay among young children, the researchers said. Yogurt is one of the products identified and highlighted for a 20% reduction of sugar by 2020.
It is important to remember that yogurts are nutritionally valuable, providing protein, calcium, iodine as well as B vitamins and many other minerals.
We know that working out the sugar content of food can be confusing because government sugar recommendations for a healthy diet only refer to "free" (also called "added") sugars, and food labels don't distinguish between free and total sugars.
Organic yogurts contained an average of 13.1 grams of sugar per 100 grams, which is roughly equivalent to three sugar cubes, while children's yogurts averaged 10.8 grams.
Less than 10 percent of the yoghurt sold in major British supermarkets is low in sugar, meaning it contains less than 5g sugar per 100g. One Yoplait yogurt, marketed with Disney's popular Frozen characters on it, contains 13 grams of sugar in a 113 gram serving.
"Helping people to understand the quantity of sugar that is in their yogurt and its possible ill effects on health may go a long way to smoothing the road for when the sugar is reduced", she noted.
The team sorted the products into eight groups including desserts, organic yoghurt, natural or Greek yoghurt, dairy alternatives and yoghurts aimed at children, including fromage frais.
The research received no specific grant from any funding agency in the public, commercial or not-for profit sectors. With 125 years of academic heritage since our founding in Battersea, and 50 years of world-class teaching and research in Guildford, the University of Surrey is the intellectual home for more than 15,200 students, 100,000 alumni and 2,800 staff.