But those who witness the effects of a poor diet say they'd like to see limits on sugar consumption and support the recommendations.

Dr. Norman Tinanoff, a pediatric dentist, said children who consume a lot of sugar tend to be fatter and shorter because they are not getting proper nutrition. They also can have cavities by the time they are 1, causing pain and necessitating sedation to fix with fillings or tooth extraction. Sometimes, a serious infection can arise.

It's the frequency of consumption that is most harmful to teeth, said Tinanoff, chief of the division of pediatric dentistry at the University of Maryland School of Dentistry. Bacteria sitting on teeth use the constant supply of sugar to produce acid that causes tooth decay.

"Some kids are eating all the time, cookies, candies, juices, sodas," he said. "Look at see how much sugar is in animal crackers and fruit juice. If you're walking around all day snacking like this you're going to get tooth decay."

Poor habits formed in youth lead to poor habits as adults. And Tinanoff said pain can make people less productive and the appearance of decay can make them less employable and sociable.

Dropping the harmful snacking and brushing twice a day with fluoridated toothpaste, even in young children, is now recommended. Tinanoff said he never brings up government guidelines, but talks about sugar consumption.

He asks parents why they think their kids have cavities and what they think they should do to prevent them "and they know the answers." He acknowledges he's not always successful.

Dr. Stephen Davis, an endocrinologist, has similar conversations with adults with diabetes. He said he doesn't demonize sugar but emphasizes the benefits of eating a balanced diet and exercising.

New guidelines can reinforce basic information people already know, but there are hurdles such as people's tastes and habits, said Davis, chairman of the department of medicine in the University of Maryland's School of Medicine.

And some information is misleading, such as small portion sizes listed on food labels, which the FDA does plan to update to make more realistic.

For now, he said the bulk of his patients do not eat right or exercise enough. Patients don't feel pressure to improve because diabetes, high blood pressure and high cholesterol don't necessarily have immediate and profound consequences.

"I don't think there is anything bad about sugar per se, but if we have too much sugar, or fat or even protein, there can be deleterious health effects," Davis said. "What we need to be doing is cutting down on our food intake and finding ways to have more physical activity. … It's tough when grabbing a soda and a bag of Doritos is the easiest and probably cheapest meal."