People are underestimating sugar levels in drinks which are perceived to be "healthy" options, according to new research.
More than 2,000 people across the UK were asked to estimate how many teaspoons of sugar were in a variety of beverages and, while many overestimated the amount in fizzy drinks, they "significantly misjudged" the levels in milkshakes, smoothies and some fruit juices.
The research, carried out by the University of Glasgow, suggested the average person in the UK consumes 659g and 3,144 calories a week through non-alcoholic liquid intake.
At 450 calories a day, it is the equivalent to almost a quarter of the recommended daily calorie intake for women and around a fifth for men.
Half of people who admitted to drinking three or more sugary drinks in a day said they did not compensate by reducing the calorie intake of their food while nearly a quarter of those surveyed did not take into consideration their liquid sugar or calorie intake when they were last on a diet.
The over-consumption of sugar-sweetened drinks contributes to obesity, which is a major risk factor for health conditions such as type-2 diabetes, high blood pressure and heart disease and stroke.
Naveed Sattar, Professor of metabolic medicine at the University of Glasgow, said: "What you drink can be as damaging to the body as what you eat and there is no question that consuming too many sugar-sweetened drinks can greatly contribute to abdominal obesity and, therefore, increase your likelihood of developing health conditions such as type-2 diabetes and cardiovascular disease.
"This analysis confirms that many people are perhaps not aware of the high calorie levels in many commonly consumed drinks.
"Some varieties of drinks such as pure fruit juices and smoothies which are perceived as 'healthy' options are also very high in sugar.
"For many people struggling with their weight, reducing their intake of such drinks and replacing with water or diet drinks would be a sensible first target to help them lessen their calorie intake.
"For some, this change might seem difficult or impossible as they admit to having a 'sweet tooth'.
"However, it is now clear that our taste buds can be retrained over time to enjoy far less sugar in drinks (or no sugar at all).
"But people deserve support and encouragement to make these changes, and the soft drinks industry also has a role to play here by providing drinks with less sugar or offering cheaper diet versions."