To some Americans, Michelle Obama’s quest to transform their diets and daily fitness consists of little more than talk-show dance routines and planting veg on the White House lawn. But while those stunts lit up social media, the First Lady’s “Let’s Move!” campaign has also pushed real, substantive changes with genuine potential to improve the nation’s long-term health.

The Obama administration, at the urging of Ms Obama’s team in the White House East Wing, imposed what amounts to a ban on harmful trans fats.To some students’ chagrin, US schools have introduced more fruits, vegetables and whole grains to their lunches. There has been a well-funded drive to provide poor communities with better access to fresh produce.

And this week, Ms Obama celebrated another hard-fought victory, as she unveiled the first changes to food nutrition labels in more than 20 years. Soon, for the first time, food companies will be obliged to list the levels of added sugar in some 800,000 products – and to tell consumers how little of it they ought to be eating.

The Nutrition Facts label – thought to be the world’s single most reproduced graphic image – has appeared on food packages since 1994. This, its first major overhaul, is expected to cost an estimated $2bn (£1.4bn), but the subsequent health benefits to consumers are believed to be worth at least 10 times that.

Food companies have two years to comply with the new rules, which were proposed by the Food and Drug Administration (FDA) in 2014 and have been in the works for at least a decade. Ms Obama’s team, however, is being given credit for helping to finally make them a reality. The First Lady announced the regulations at an annual nutrition summit in Washington DC on Friday. “You will no longer need a microscope, a calculator, or a degree in nutrition to figure out whether the food you're buying is actually good for our kids,” she said.

Her sentiments were echoed by health groups such as the American Heart Association, whose CEO Nancy Brown said in a statement: “Clear, easy-to-understand food labels will help put Americans on the path to healthy eating.”

The goal of “Let’s Move!” is to end childhood obesity in the US, where the Centres for Disease Control and Prevention estimates 17 per cent of young people and a third of all adults are now obese. The campaign has brought Ms Obama into direct conflict with food companies, particularly in her effort to highlight the amount of added sugar in processed foods.

Perhaps unsurprisingly, the foods that contain the most added sugars include soft drinks, sweets, cakes and ice cream. The Sugar Association, a trade group that represents sugar producers, claims added sugar is no less healthy than the sugar that occurs naturally in foods, and that to single it out in labeling sets “an alarming precedent”.

Many processed food producers are already struggling to respond to a decrease in demand for unhealthy drinks and snacks as US consumers become increasingly conscientious about their diets. Some US cities are considering imposing taxes on soft drinks, and this summer San Francisco will introduce health warnings on all sugary beverages.

Yet some major food companies have come out in support of the new labelling measures, including Mars, whose vice president of public affairs, Brad Figel, said the firm “applauded” the changes, calling them “a major step forward in giving customers more transparency”.

At first glance, the new nutrition labels will appear almost identical to their predecessors. In 1994, fat was the most feared part of foods, now it is calories, which henceforth will be listed in a much more prominent font.

The labels will also divide added and natural sugars, and include a new percentage of the recommended daily value for added sugars. Current guidelines suggest consuming no more than 10 per cent of daily calories in from added sugar: a limit equivalent to about 50 grams of sugar per day, meaning most canned soft drinks would alone contain significantly more than the daily value for added sugars.

Meanwhile, serving sizes for many foods are being increased to more closely resemble the helpings that most Americans really eat. For instance, a pint-sized tub of ice cream will now be labelled as three servings, instead of the traditional four.

In a blog post, FDA administrator Dr Robert Califf explained: “In addition to added sugars, new nutrients that must be declared include Vitamin D, which is important in bone development, and potassium, which is good for controlling blood pressure; both nutrients of which people aren't getting enough,”