Want to drop a few pounds before that big date on Friday? Feeling the need to lose weight to boost your athletic performance? Many people look for fast or easy ways to slim down at some point in their lives. And there are hundreds of diet plans out there to lure you. But before you choose between the all-juice diet and the no-carb diet, read on to find out exactly what these diets do - and don't do - for you.
What Are Popular Weight-Loss Plans and How Well Do They Work?
Commercial weight-loss plans typically fall into two categories: Those that drastically reduce a person's calorie intake or restrict the dieter to certain foods and those that require a person to take dietary supplements. Dietary supplements are usually pills, but they sometimes include special food bars or drinks.
Most of the popular diets on the market today rely on a person's natural tendency to want to lose weight quickly. They play into a desire for fast results, which is what happened to Jamie, 16, who followed a 5-day juice diet. Although Jamie lost the weight she wanted, a week later the scale showed she was back to her original weight.
It's quite common for people to quickly gain back all the weight they lose after a few days on a highly restrictive diet. Here's a doctor's answer on why: "The first thing to be aware of with quick weight-loss diets is that our bodies simply aren't designed to drop pounds quickly," says Steven Dowshen, MD, an expert in hormones and the endocrine system. In fact, doctors say that it's nearly impossible for a healthy, normally active teen or adult to lose more than about 3 pounds per week of actual fat from their bodies, even on a starvation diet.
So why does your scale tell you otherwise? "The trick these very low-calorie diets rely on is that your body's natural reaction to near-starvation is to dump water," Dr. Dowshen says. That means that most, if not all, of the weight you lose during the first few days on these diets is water, not fat. You may feel thinner, but you won't look it and you'll probably bounce back up to your original weight once you start eating normally again. "What these diet plans don't tell you is that your body will just suck this lost water back up like a sponge once you start eating more calories again," Dr. Dowshen says.
Losing water weight is also the key to the quick weight-loss claims of some of the diet pills on the market. Many of these pills contain laxatives or diuretics - ingredients that force a person's body to eliminate more water. Other diet pills rely on ingredients that claim to speed up a person's metabolism (the process by which the body turns food into energy and stores unused calories as fat); suppress appetite; or block the absorption of fat, sugars, or carbohydrates.
Do these types of supplements actually do what they say they will? Unfortunately, there's usually no reliable scientific research to back up the claims provided by the product's manufacturer. In addition, there are many unknowns about the substances used in diet supplements, so dietitians and doctors consider them risky. What research studies do show is that most of the people who try one of these "crash" diets regain all the weight they lost within a few weeks or months.
Do These Diets Put Your Health at Risk?
Luckily, very few people stick to a highly restrictive diet for long periods of time and most people give up on them after a few days. But what happens if you keep following extremely low-calorie diets or taking weight-loss supplements? That's when things can get a little scary.
Radically cutting back on calories can make you tired, jittery, and moody. These symptoms usually go away when you resume healthy eating habits, but over the long term, a highly restrictive diet may cause other health problems. You may lose some of your hair, your fingernails may become brittle, dark circles may appear under your eyes, and your muscles may shrink and weaken. Sometimes staying on a highly restrictive diet for a long period of time can cause lasting damage to your body, especially to the heart and kidneys. Following extreme diets over the long term or a pattern of extreme dieting followed by binge eating are both signs that a person may have an eating disorder.
Drastically reducing your food intake depletes the body's access to the vitamins, minerals, and fiber that it needs to stay healthy. If a diet requires you to cut out all dairy products, for example, you are also losing valuable calcium. Over a prolonged period, a lack of calcium puts a person at increased risk for osteoporosis (pronounced: ahs-tee-oh-puh-ro-sis), a condition in which bones become brittle and more susceptible to injury as a person ages. Some diets - like those that omit all red meat - may leave the dieter lacking iron, which can lead to anemia, especially in teen girls. And trying to replace the foods you're cutting out with vitamin pills is a bad idea. Foods like fruits and vegetables contain more than just vitamins and minerals - they are some of the best sources of fiber. Fiber can help to prevent disease.
Restricting food intake over a long period during a person's teenage years can stunt growth. Following restrictive diets over a long period can also delay some of the changes associated with puberty, such as breast development in females and muscle bulk in males. Another side effect of restrictive diets in teenage girls is irregular menstrual periods - or even not getting a period at all.
Another effect of very low-calorie diets is a decrease in resting energy expenditure, or the amount of calories a person burns at rest. One reason for this "slower metabolism" is that people on restrictive diets often lose muscle mass, and muscle burns more calories than fat - even while a person is resting. This makes continuing to lose weight even more difficult and regaining weight easier.
What about the long-term effects of taking diet pills? Common ingredients in diet pills include caffeine, alcohol, 5-hydroxytryptophan (5-HTP), chromium (or chromium picolinate), phentermine, and vanadium. These ingredients may carry health risks for certain people. Ephedrine (also known as ephedra or ma huang), an ingredient in many diet and sports supplements during the late 1990s and early 2000s, was linked to heart problems and may have played a role in the death of at least one professional athlete. The U.S. Food and Drug Administration decided the health risks associated with ephedra were too great, and it banned the substance in December 2003.
If you have any health conditions or are taking medication, always check with your doctor before taking weight-loss supplements because the ingredients in some supplements may interact with specific drugs. For example, 5-HTP may cause adverse reactions in people who take certain medications for depression.
Even ingredients that seem like a normal part of your diet can carry risks when used in weight-loss pills or other stimulants: For example, the average caffeine-based weight-loss pill contains as much caffeine as 6 cups of coffee. Imagine how wired you'd be if you took two or three of these pills each day! The side effects associated with these products include rapid heart rate, increased blood pressure, dizziness, sleeplessness, seizures, and even addiction.
Furthermore, it's important to know that most diet supplements have not been tested on teen users. Not only does this mean that the dosages prescribed may not be accurate, it could mean that taking certain supplements might carry unknown risks for teens.
How Can You Lose Weight for the Long Term?
Regardless of concerns about the effectiveness and safety of restrictive diets, keeping the pounds off long term should be the major goal for anyone who wants to lose weight - and that can be more challenging than losing them in the first place. Weight loss is most likely to be successful and lasting when a person changes his or her habits to reduce the overall number of calories he or she eats while at the same time increasing the number of calories burned through exercise. Exercise not only burns calories, it also builds muscle. The more muscle you have, the more efficient your body becomes at burning calories, even when you aren't exercising. You don't have to become a gym rat, though: Walking the family dog, cycling to school, and doing other things that increase your daily level of activity can all make a difference.
Research confirms that one reason people get less exercise these days is because of an increase in "screen time" - in other words, the amount of time spent watching TV, looking at the computer, or playing video games. The American Academy of Pediatrics recommends limiting all screen time to 1 hour per day. If you're hanging with your friends at the mall instead of chatting to them on the computer, for example, you're getting more exercise.
A survey on health and nutrition conducted by the Centers for Disease Control and Prevention shows that serving sizes for both kids and adults have increased over the past 10 years, and that this is a contributor to obesity. If you super-size your fries or always go for extra hot fudge on your sundae, you are probably taking in more calories than your body can use. Another key dietary factor in weight gain today is the increased consumption of flavored beverages, such as sodas, sweetened juice drinks, and sports drinks. Some people keep a food diary to track what they eat and drink. Writing everything you eat in a daily diary might help you identify those hidden foods that contribute to unwanted weight gain - like the candy bar you usually munch between third and fourth period.
The best way to build a weight-loss program that's right for you is to talk to your doctor or a registered dietitian. During your appointment, your doctor or dietitian may ask you what types of foods you eat, how much weight you want to lose, and the reasons why you want to lose weight. He or she will also help you figure out approximately where your weight should be based on your height and other factors and suggest a sound weight-loss plan that meets your individual needs. (Dietitians report that most guys and girls find weight-loss plans that take their daily schedule and food preferences into account are easier to follow.) The eating plan must include enough calories per day to keep your body working and developing properly. And if you're cutting calories to lose weight, your body will still need to get the same amount of nutrients to stay healthy.
Staying active is an important part of keeping off the weight you've lost. If you achieved your weight-loss goal by eating a variety of foods in smaller portions and exercising regularly, chances are better that you will stick with a healthier lifestyle and keep the pounds off in the long run.
Reviewed by: Julie Metos, MPH, RD, CDE
Date reviewed: January 2004