Eating a meal made with "slow-release" carbohydrates, such as oatmeal or bran cereal, before you exercise may help you burn more fat, suggests a recent study in the Journal of Nutrition. Researchers assessed the rate of fat burn among eight healthy women after they ate two breakfasts: muesli with milk, peaches, yogurt and apple juice on one day; cornflakes with skim milk, white bread with margarine and jam and an energy drink on another day. Both meals contained similar amounts of calories. The first breakfast (muesli) was a low-glycemic-index (GI) meal, the second was a high-GI meal. The glycemic index ranks foods based on how much they raise blood sugar. Lower-GI foods produce smaller spikes than higher-GI foods. Generally, foods that contain protein, fat and/or fiber and are digested more slowly fall lower on the GI scale than those that consist mostly of carbohydrate (e.g., white bread). On the days when the women ate the low-GI breakfast, they burned nearly twice as much fat during a 60-minute walk as they did on the days when they ate the high-GI meal. Here’s why: Because the muesli (low-GI) breakfast was more slowly digested, it didn’t spike blood-glucose levels as high as the cornflake (high-GI) breakfast did. In turn, insulin levels didn’t spike as high either which probably explains why the muesli-eating women burned more fat, says Ian MacDonald, Ph.D., director of research at the University of Nottingham Medical School. Insulin plays a role in signaling your body to store fat. So, lower levels of insulin might help you to burn fat. Bottom line: If you’re looking to burn more fat, pick low-GI foods, such as oatmeal, over high-GI foods, such as white toast, before your workout.

Mona Lisa’s Mysterious Smile Now You See It, Now You Don’t.

Any list of the world’s top ten most famous paintings will surely include da Vinci’s Mona Lisa. Part of the painting’s appeal is its mystery.

Those lucky enough to have an unobstructed view of the Mona Lisa at the Louvre often stare in awe, baffled by the smile that seems to flicker and fade. Gazing at a reproduction of the work produces the same effect. Now she’s smiling, now she’s not.

What’s the deal with Mona Lisa’s smile?

Harvard neuroscientist Margaret Livingstone is pretty sure she’s solved the puzzle. Presuming nothing, Livingstone reasoned that the famous portrait’s flickering smile is caused by the way we see.

Our eyes use two separate regions to see. One is the fovea, a central area used to see colors and pick out details such as fine print. The area around the fovea is better at detecting motion, shadows, and stark, black and white contrasts.

When we look at a person’s face, according to Livingstone, we usually focus centrally on the eyes. Gazing at Mona Lisa’s eyes, our less accurate peripheral vision notices the mouth, picking up shadows from the cheekbones.

The shadows play visual tricks, hinting at the curve of a smile. But when we look directly at the mouth, our central vision doesn’t see the shadows, and so the smile suddenly disappears. As our eyes scan different parts of the portrait, Mona’s smile seems to fade in and out.

Did da Vinci intend to create this flickering smile effect? Perhaps. In any case, he was genius enough to paint shadows subtle enough to astound viewers for half a millennium. Meanwhile, Mona Lisa will keep smiling. And not.