Today's Globe: summer obesity, healthcare rules, weight and heart health, vitamin D, healthcare costs, Stop & Shop tuna, heart devices

Taina Pena, 9, of the South End worked out on an exercise machine at Body by
Brandy fitness studio in Boston. (Erik Jacobs for The Boston Globe)

It is the paradox of summertime: The very months blessed with the greatest opportunity for running and jumping and playing have instead become prime time for packing on pounds.

Businesses are balking at a proposed state regulation that, a leading retail group says, will force small companies to spend thousand of dollars more in health insurance for their workers, and could lead many employers to drop coverage altogether.

You can look great in a swimsuit and still be a heart attack waiting to happen. And you can also be overweight and otherwise healthy. A new study suggests that a surprising number of overweight people - about half - have normal blood pressure and cholesterol levels, while an equally startling number of trim people suffer from some of the ills associated with obesity.

Adults with a vitamin D deficiency are more likely to die than adults who have high levels, another indication of the nutrient's vital role in guarding against ailments from heart disease to cancer, US researchers said yesterday.

Healthcare costs are expected to rise more than 10 percent into next year, according to a survey of insurers by Aon Consulting Worldwide, the smallest Aon has seen in six years.

Stop & Shop is voluntarily recalling tuna salad because it could be contaminated with Listeria.

Fewer than half of eligible patients in the United States received medical devices to shock their faulty hearts back into rhythm, though the products can cut death rates by more than one-third, a study found.