My partner and I have been together for 15 years. We're healthy and exercise regularly. However, he wanted to lose some of his excess belly fat that bothered him. He ramped up his exercise routine, began to eat fewer refined carbohydrates (like white flour and white pasta), consumed more lean meat, vegetable proteins, and dark leafy vegetables. Eventually, he lost nearly 15 pounds but plateaued and couldn't lose any more.
Something wasn't right, something more had to change.
When I met him, one of the first things I noticed in his fridge was a 2-liter bottle of sugar-filled soda, sometimes two or three bottles. During the day, he would often gulp down a full bottle of soda. And there were those ultra-sweetened cereals he ate as well as Pop-Tarts, which were his go-to work snack.
All this was new and a bit alarming for me. I grew up in India, where I had minimal exposure to processed or packaged foods. There are unhealthy Indian foods, savory and sweet, but my parents (fortunately) knew better and limited their availability in our home, so I never cultivated a habit for such things.
One day, I checked out the sugar content on the 2-liter soda bottle and cereal box. (I always had an in-built curiosity about food labels and contents of packaged foods.) I was shocked to learn that my partner was typically consuming about 200 g of sugar (around 800 calories) daily, just from the soda! Intuitively, I didn't think “excessive” consumption of added sugars could be good for anyone.
Because sugar provides empty calories with no nourishment for the body, it has no “recommended” intake value. Even though an occasional sugar treat is okay according to most health professionals, the American Heart Association (AHA) has a maximum intake allowance for sugar. According to AHA, women should have no more than 6 teaspoons of sugar (25 g) per day or 100 calories of sugar. Men can go up to 9 teaspoons (38 g) per day, which is about 150 calories. Even this sounds excessive to me! Understandably, this varies by age, sex, and activity level. 
No matter what your gender, a single 12-ounce can of Coke goes over the maximum daily allowance for sugar. Clearly, my partner's consumption of sugar was questionable.
Even though the jury is still out on a specific causal link between added sugars and health risk markers , mounting evidence suggests these sugars (not just fructose ) may be related to increased risk of weight gain, and relatedly, the development of a complete metabolic syndrome (frequently, lifestyle-related diseases). 
I cautiously suggested that he try cutting back on his sugar consumption. He acknowledged that he had too much sugar in his diet but didn't see it as a health concern. About a year later, out of the blue, he told me that he was giving up his sugary drinks and supremely sweet snacks. I was puzzled but happy.
What motivated this move to go “cold turkey” on sugar after years of consuming at least 2 liters of soft drinks per day? A combination of my “advice” and his own realization that to lose more weight he needed to cut the added sugars, which are just empty, nutrition-less calories.
Interestingly, after cutting back on sugary drinks and food, he had more energy, he didn't feel constantly hungry, and he lost 30 lbs in about a year. This is not to say that everyone will have the same results from dropping sugary drinks from their diet, but it emphasizes the importance of being open to a change in diet to see what works best for you.
Ultimately, working toward any lifestyle change for better health takes time, commitment, and emotional support from loved ones, despite normal setbacks along the way. Having the intention to change certain habits and working towards those, like my partner did, definitely helps, too!
1. Hitti, Miranda. August 2009. “Heart Group: Limit Added Sugars in Diet.” http://www.webmd.com/diet/news/20090824/heart-group-limit-added-sugars-diet
2. Rizkalla, S.W. 2010. “Health Implications of Fructose Consumption: A Review of Recent Data. Nutrition and Metabolism.” 7; 82. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2991323/
3. Parker-Pope, Tara. September 20, 2010. “In Worries about Sweeteners, Think of All Sugars.” New York Times. [http://well.blogs.nytimes.com/2010/09/20/in-worries-about-sweeteners-think-of-all-sugars/]
4. Nseir et al. 2010. June 7. “Soft Drinks Consumption and Nonalcoholic Fatty Liver Disease.” June 7: 16 (21). http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880768/
Bray et al. 2004. “Consumption of High-Fructose Corn Syrup in Beverages May Play a Role in the Epidemic of Obesity.” American Society of Clinical Nutrition. http://ajcn.nutrition.org/content/79/4/537.full