The phrase "a source of calories" is correct and usable in written English.
It can be used when discussing food or nutrition, specifically referring to items that provide energy in the form of calories.
Example: "Fruits and vegetables are important for a balanced diet, but nuts and seeds are also a significant source of calories."
Alternatives: "a calorie provider" or "a calorie contributor".
One reason for the new study, Dr. Nielsen said, was to quantify a source of calories that Americans rarely give much thought to.
The panel of experts said the main impact of sugar on health was as a source of calories in the diet that can lead to obesity.
"Certainly our regular soft drinks are a source of calories, so if you're consuming too many calories and watching too much television or not getting enough exercise, you're going to have a problem".
This is the science of nutrigenomics -- which describes how food is information that tells our bodies what to do, not just a source of calories we need for energy.
Before the 1930s, dietary fat was thought to be simply a source of calories which could be exchanged by e.g. carbohydrates.
In the tropics, cassava ranks third as a source of calories, and is typically grown by resource-poor smallholder farmers on marginal lands.
And while exercise may induce brown fat in humans, it remains to be seen how important a source of calorie burning it is, researchers say.
Alcohol is often called a source of "empty calories", and for good reason - alcoholic beverages like beer, wine, and liquor contain calories but little in the way of actual nutrition.
As energy-dense foods, nuts can easily become a source of excess calories, especially nibbled semiconsciously, However, when nuts and nut products are included in a calorie-controlled diet, they may actually improve dieting success.
Drinks, too, can be a source of pointless calories.
The alcohol may also have served as a source of important calories.
