Blake Lively, Jessica Alba and Jennifer Lopez are among the celebrities who've supposedly jumped on the juicing craze. The juice isn't responsible for their enviable bods, however. Fresh-pressed juices are an expedient way to consume fruits and vegetables, but juices don't have any notable metabolism-boosting properties. You're better off eating whole fruits and vegetables, which contain the same nutrients as plain juice but still have the natural fiber to make you feel full. Round out your healthful diet with lean proteins, whole grains, unsaturated fats and low-fat dairy, and focus on upping your physical activity. Exercise helps boost your metabolism more than any natural juice combination will.
Your metabolism consists of three primary parts. Your resting metabolic rate, or RMR, which makes up about 60 percent of your metabolism, is the number of calories you use daily for essential bodily functions, such as breathing and pumping blood. Physical activity can comprise as much as another 30 percent of your metabolism. Formal exercise, as well as everyday actions such as bathing and walking around the office, count toward this part of your calorie burn. The final 10 percent of your metabolism is called the thermic effect of food -- the calories your body uses to digest food and process its nutrients.
Although they aren't found in juice, some food ingredients -- including caffeine, tea and capsaicin from hot peppers -- may modestly increase your metabolic rate for short periods of time. Protein has a high thermic effect, which means your body burns more calories to digest high-protein foods, according to a study published in The American Journal of Clinical Nutrition in 2008.
Capsaicin is the only one of these ingredients that has proven metabolic-boosting benefits and integrates pretty readily into some juice recipes. Capsaicin is the compound in hot peppers that gives them their intense, spicy bite. Consuming red pepper as part of a meal increased energy expenditure and promoted a higher body temperature in study subjects, reported a 2011 study in Physiology and Behavior. The higher calorie burn lasted for about 4 1/2 hours after the meal, during which participants burned 10 additional calories compared to people who did not consume red pepper.
To keep calories low, use a variety of veggies and hot peppers in your natural juice recipes. The hotter the pepper, the greater the capsaicin content, but too much hot pepper could make your drink intolerable. When you're blending your juice, add small slices gradually until you reach the desired intensity.
Try a little fresh cayenne, habanaro, jalapeno or serrano pepper added to a green mix of kale, cucumber, lemon and green apple or juiced with pineapple, lime and spinach makes for a spicy juice that revs your metabolism just a bit. Or make a low-calorie, spicy juice that plays on the bloody Mary cocktail. Juice tomatoes, lemon and celery and stir in a pinch of powdered cayenne pepper for extra kick.
For another spicy, tomato-based mixture, blend cherry tomatoes, celery, carrots, spinach, cilantro, arugula, garlic, lemons and jalapeno. Stir in a drizzle of honey if your mix comes out too bitter for your taste.
An Asian-inspired juice uses hot serrano peppers, celery, sugar snap peas, scallions, red bell pepper, cherry tomatoes and lime. Finish with a splash of refreshing coconut water.
Although natural juices taste fresh and nourishing, juicing may actually have negative effects on your metabolism. A juice fast, where you consume only fresh juices for days on end, seems like a quick way to reduce your calorie intake. But, when you take in too few calories and don't exercise, your system responds by decreasing your metabolism by as much as 20 percent, reports researcher Andrew J. Hill in a 2004 issue of the British Journal of Nutrition. A juice fast also denies you protein, which is counterproductive, because getting enough protein benefits your metabolism.
Simply adding natural juices to your existing diet may sabotage your weight-control goals. Juice, especially when made primarily with fruits, can be quite calorie dense and doesn't register as satiating, so you'll still feel hungry enough to eat all of your food at meals. Adding calories from the juice to your existing intake may create a calorie surplus that causes you pack on pounds.
When juice is extracted from the whole fruit or vegetable, it leaves the fiber behind. That's too bad, because fiber helps regulate digestion and provides increased satiety, which may help you eat less. Another disadvantage of juice, especially if it's made predominantly with fruit, is that it's packed with carbohydrates -- in the form of sugar. Consuming sugar-laden beverages, compared to drinks with a balance of nutrients, can work against weight loss. In one study, subjects who consumed sugary drinks had less feelings of satiation and burned fewer calories digesting the drink than those who drank a beverage containing a mix of protein, carbs and fat. These results were reported in a study published in a 2004 issue of the International Journal of Obesity and Related Metabolic Disorders.
An occasional fresh juice drink can be a nutritious addition to your diet, but it can't replace other metabolism-boosting strategies, such as strength-training. Lift weights to add muscle mass, which requires significantly more energy to maintain compared to fat tissue. Move as much as you can all day. Formal exercise helps burn calories, but so do small movements -- known as non-exercise induced thermogenesis, or NEAT. Tapping your foot, walking to the water cooler, climbing stairs and doing laundry are examples of NEAT that boost your calorie burn.
Eating at regular, predictable intervals during the day can also maximize the thermic effect of food. Participants who consumed the same number of meals per week with the same number of calories, but in an erratic pattern, experienced a lower calorie burn after meals than people who ate at six regular intervals, showed a 2004 study in the International Journal of Obesity and Related Metabolic Disorders. Do your best to eat each meal around the same time daily and snack on healthy foods between meals. Quality snacks include whole fruits and vegetables, a scant handful of raw nuts or low-fat yogurt.