More and more obese people – that is, those with a body mass index greater than 30 – are resorting to weight loss pills to return to healthy weight. In most cases, prescription pills are preferred over “OTC” pills since the former are more often regulated and tested by the Food and Drug Administration (FDA) and thus are considered to be safer. However, it must be noted that every weight loss pill, let it be prescribed or over-the-counter, causes unwanted health effects.

Some popular FDA-approved prescription drugs are:

1. Xenical: It prevents the absorption of fat into the body and thus causes weight loss. It also causes nausea, vomiting, and loose and oily stools.

2. Meridia: It is used as a short-term appetite suppressant in conjunction with a low-calorie diet. It also causes some undesirable health effects such as headache, constipation, fatigue, insomnia and anxiety. Many people are also allergic to this drug.

3. Phentermine: It also acts as an appetite suppressant. Some of its side effects are insomnia, diarrhea, nausea, vomiting, nervousness and headaches.

There is also one – and the only – over-the-counter weight loss pill called the Alli. It is used in combination with a low fat diet and regular physical activity. Alli and Xenical work similarly. However, the ingredient orlistant in Alli is known for causing extreme diarrhea and oily spotting.