What undesirable effects are seen with the use of diet pills?

The use of diet pills can often lead to nervousness and sleep disturbances due to the stimulant properties commonly found in many of these products. Many diet pills are formulated with ingredients like caffeine or other stimulants that can increase heart rate and lead to feelings of jitteriness or anxiety. These effects can interfere with normal sleep patterns, causing insomnia or poor-quality sleep, both of which contribute to increased nervousness.

In contrast, the other options do not accurately reflect the typical side effects associated with diet pills. While visual disturbances and headaches may occur with some medications, they are not as characteristic of diet pill use. Increased alertness and cognitive function might be a temporary effect from stimulant ingredients but are not a desirable outcome of diet pill usage and can contribute to other negative feelings. Extreme feelings of congestion are also not generally linked to diet pills and could be more related to allergies or other underlying conditions. Thus, nervousness and sleep disturbances are the most directly associated side effects of diet pills.