For a variety of reasons, black tea can contribute to weight loss as long as you drink it unsweetened. Although this makes it an inexpensive and effective weight loss supplement, unsweetened black tea can be hard on the palate. A squeeze of lemon juice adds flavor to make it easier to drink, without injecting so many calories that it derails your weight loss efforts.
Black Tea Basics
Black tea is a "true tea," meaning it's made from the leaves of the Camellia sinensis plant. When making black tea, processors allow the picked leaves to ferment in open air for a period before drying and curing. You steep the leaves in boiling water for about five minutes, then drink the tea hot or over ice.
The caffeine in black tea is a stimulant. Stimulants push your body to be more active and boost your metabolism so that you burn more calories in all activities. Caffeine is also a mild appetite suppressant. This means black tea can help you lose weight by stimulating you to burn more calories while simultaneously getting you to eat fewer calories throughout the day. Since lemon juice doesn't interfere with your body's absorption of caffeine, it should not reduce this effect.
Caffeine is also a diuretic, a substance that stimulates you to urinate more often and in greater amounts. This can lead to water weight loss, which makes a difference on your bathroom scale. Lemon juice is also a diuretic, according to information at Purdue University's horticulture website. However, water weight loss is temporary. It will return as soon as you restore a healthy level of hydration.
Catechins are micronutrients found in black and other teas. A variety of studies, including one from 2005 published in "Bioscience, Biotechnology, and Biochemistry," demonstrate that catechins interfere with the body's ability to absorb fat. According to Dr. Stephen Pratt's SuperFoods website, the research on catechins has focused on its effects in animals and on blood serum cholesterol, not on weight loss in humans. However, any process that blocks your body's absorption of calories may contribute to weight loss. As of 2011, no research has been conducted on whether or not lemon juice has any effect on this process.
In a column for CNN Health, Dr. Melina Jampolis reports that drinking a zero-calorie beverage before each meal can influence you to reduce your food portions enough to lose more than a pound per month. Unsweetened black tea contains no calories. Lemon juice contains about 8 calories per ounce, according to the USDA nutrition database. Although that would technically make your tea no longer a zero-calorie beverage, it's not enough to completely counter the weight loss benefits it provides in terms of portion control.