Considering that man needs about 3 liters of water every day for maintaining the moisture balance in the body, food and beverages provide a major part of this through the diet, rest coming from drinking water. While water by itself does not contribute to any calories, foods and beverages contain calories contributed by carbohydrates, fat and proteins to varying extent depending on their concentration. Beverages based on fruits, vegetables, herbs, sugar, alcohol and milk offer a wide variety competing for the minds of the consumer. The calorie contents in these beverages are influenced by the extent of metabolizable carbohydrates like sucrose, high fructose syrup or other natural sweeteners. Sugar content in most of the beverages can vary from 10% to 20% depending on the source or the recipe. Alcoholic beverages like wine derive the calories from sugar as well as alcohol while others like hard liquor or beer have only alcohol to contribute to calories.
Soft drinks including aerated beverages are usually based on white sugar or high fructose corn syrup (HFCS) and are at the center of controversy regarding their role in uncontrolled weight gain. HFCS is increasingly being implicated in obesity in the US probably because of the large consumption base for such drinks in that country. Compared to India where the per capita soft drink consumption is a "healthy" 2 liters per year, corresponding figure for the US is around 190 liters in 2005 and shockingly this figure is almost 100% jump from that in 1980. In contrast total milk intake dropped from 95 liters per capita per year in 1980 to less than 70 liters in 2005! How far this shift in consumption pattern is responsible for the current day health problems in that country is a matter of conjecture. How ever it is well recognized that soft drinks are high in Glycemic Index (GI) and Glycemic Load (GL)while milk has significantly lower values for GI and GL.
The caloric density and quantum of foods consumed determine the extent of calories ingested and unless calorie intake is balanced with its expenditure through physical activity, excess will invariably cause body weight increase. Though pure sugar and pure fat, when taken directly will have highest caloric density (CD), products containing these ingredients in varying proportions can have different CD values. Theoretically solid foods should always be high in CD values because of higher metabolizable solids but their consumption is self limiting due to satiety factor and limitations vis-a-vis oral cavity, moisture content and gastrointestinal capacity. In comparison liquid foods are easily consumed and metabolized fast in the body creating more cravings for beverages. It is believed that fluid calories do not give a strong feeling of fullness and consequently more food is consumed to get the satiety resulting in higher consumption of calories unintentionally. A person drinking an alcoholic beverage or a soft drink before a meal usually does not compensate for these extra calories by consuming less food at the table, a major reason for higher calorie intake.
Looking into the development of soft drink industry world over, 4 out of 10 top selling grocery items in most of the developed countries belong to the beverage category which includes soft drinks, juices, milk and beer and sugar sweetened juices account for more than 35% of the beverages on the market shelves. Though both 'solid' and 'liquid' calories are associated with weight changes, only reduction in the intake of sugar sweetened beverages is translated into significant weight loss in many cases. The logical question that arises is whether one can lead a healthy life without the fear of gaining undue body weight by avoiding regular consumption of sugar sweetened drinks? Many experts think so and advocate drinks which are not sweetened like unsweetened versions of juices, coffee and tea, low calorie beverages or plain water when ever necessary. Drinking 1 or 2 glasses of water before a meal also reduces the quantity of food eaten resulting in lesser calorie intake and better health in the long run.