Sugary drinks play a major role in the obesity epidemic. Sugary beverages cannot make you feel as full as the same amount of whole foods with a similar caloric value would. According to a 2011 study published in the International Journal of Obesity, individuals consuming sugary beverages do not cut down their caloric intake by consuming less food.

Sugary drinks (sports, soda, and energy drinks) are the top calorie source in the diet of the average teen (226 calories a day), per the National Cancer Institute.

Fruit juice is not a better option. Even though fruit juice contains more nutrients than other sugary beverages, it has as much sugar and calories as any other soft drink. A 2014 study revealed that people consuming sweetened beverages, whether low- calorie or not, are inclined towards lower dietary quality.

The average can of fruit punch or sweetened soda contains about 150 calories, most of which is extracted from sugar, usually from high-fructose corn syrup. This amount is equivalent to 10 teaspoons of table sugar. If you are consuming sugar-sweetened soft drinks on a regular basis and not cutting back your caloric intake elsewhere, you could gain approximately 5 pounds a year. Drinking sweetened sodas or fruit juice, instead of water, is associated with lower, but long-term weight gain, as per the International Journal of Obesity.

A recent study in 2013 showed that the consumption of sweetened beverages has increased and may play a vital role in metabolic syndrome, fatty lever disease, and obesity, whereas cutting back on the intake of soft drinks has a close association with less weight gain, along with metabolic improvement. 

The more ounces of sweetened drinks an individual consumes each day, the more calories he or she has during the later part of the day. This is completely opposite to what happens with solid food, as individuals are inclined towards compensating for a large meal by taking in fewer calories later in the day. This compensatory effect somewhat vanishes after consuming soft drinks, for different reasons:

• Fluids are not capable of providing the same feeling of satisfaction as solid foods, as our body does not register calories of liquids, similar to calories belonging to solid foods. This might encourage an individual to keep eating even after a dose of a high-calorie drink.
• It is possible that soft drinks tasting sweet, regardless of whether sweetened with calorie-free sugar substitute or sugar, might stimulate one`s appetite for other high-carbohydrate and sweet foods.
• Even though soda may have more sugar than a cookie, as people perceive soda as a drink and cookie as a dessert, they tend to limit more food than beverages.

From all of the above factors, it can be noted that sugary drinks indeed stimulate weight gain.

References:

National Cancer Institute. Mean Intake of Energy and Mean Contribution (kcal) of Various Foods Among US Population, by Age, NHANES 2005–06.

Pan A, Malik VS, Hao T, Willett WC, Mozaffarian D, Hu FB. Changes in water and beverage intake and long-term weight changes: results from three prospective cohort studies. Int J Obes (Lond). 2013.

Bray GA, Popkin BM. Calorie-sweetened beverages and fructose: what have we learned 10 years later. Pediatr Obes. 2013;8:242-8.

http://www.hsph.harvard.edu/nutritionsource/healthy-drinks/sugary-drinks/ (accessed on 02/10/2015)

http://www.andeal.org/files/Docs/NNSResourceDraft3.pdf (accessed on 02/10/2015)

http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/child_nutrition_juices_and_sweet_drinks?open (accessed on 02/10/2015)

http://www.hsph.harvard.edu/nutritionsource/sugary-drinks-fact-sheet/ (accessed on 02/10/2015)

Helpful Peer-Reviewed Medical Articles:

Malik, V. S., Schulze, M. B., & Hu, F. B. (2006). Intake of sugar-sweetened beverages and weight gain: a systematic review. The American journal of clinical nutrition, 84(2), 274-288.

Schulze, M. B., Manson, J. E., Ludwig, D. S., Colditz, G. A., Stampfer, M. J., Willett, W. C., & Hu, F. B. (2004). Sugar-sweetened beverages, weight gain, and incidence of type 2 diabetes in young and middle-aged women. Jama, 292(8), 927-934.

Malik, V. S., Popkin, B. M., Bray, G. A., Després, J. P., & Hu, F. B. (2010). Sugar-sweetened beverages, obesity, type 2 diabetes mellitus, and cardiovascular disease risk. Circulation, 121(11), 1356-1364.

Malik, V. S., Pan, A., Willett, W. C., & Hu, F. B. (2013). Sugar-sweetened beverages and weight gain in children and adults: a systematic review and meta-analysis. The American journal of clinical nutrition, 98(4), 1084-1102.

Berkey, C. S., Rockett, H. R., Field, A. E., Gillman, M. W., & Colditz, G. A. (2004). Sugar‐added beverages and adolescent weight change. Obesity research, 12(5), 778-788.

Fowler, S. P., Williams, K., Resendez, R. G., Hunt, K. J., Hazuda, H. P., & Stern, M. P. (2008). Fueling the obesity epidemic? Artificially sweetened beverage use and long‐term weight gain. Obesity, 16(8), 1894-1900.