Each slice of grapefruit you add to your salad acts like a match to spark your body’s fat-burning ability. A study published in the journal Metabolism found that those who ate grapefruit for six weeks lost a full inch off their waistlines. What’s behind the belt-tightening effect? The fruit is rich in phytochemicals, bioactive compounds that recent research shows stimulate the production of a hormone called adiponectin, which is involved in the breakdown of body fat. Japanese research suggests the smell of the juicy fruit can “turn on” calorie-burning brown fat cells, promoting the breakdown of body fat while reducing appetite.
But you'll lose the most fat by doing HIIT, or high-intensity interval training. This training technique involves working at full throttle for short intervals -- typically 10 seconds to a minute -- then recovering at a slow pace or resting for a minute or two. It increases your metabolism after a workout, since your muscles need to work hard to get "back to normal." HIIT also burns more belly fat than traditional, steady-pace cardio, according to Penn State University.
Don’t let extra hours lounging in bed stand between you and a flatter stomach. While getting enough sleep can help boost your metabolic rate, sleeping in may undo any benefit you’d enjoy from catching a few extra winks. One Obesity study reveals that late sleepers who snoozed past 10:45 in the morning ate nearly 250 more calories over the course of the day, despite eating half as many fruits and vegetables as their early bird counterparts. Even worse, they chowed down on more salty, sugary, and trans-fat-laden fast food than those who woke up earlier. If you happen to head out of the house early, you’re in for an additional metabolic boost; researchers at Northwestern University have found that people exposed to just a short period of early morning sunlight had lower BMIs than their late-waking counterparts.