Most popular diets are considered fad diets. There is no clear definition for what constitutes a fad diet. Merriam-Webster defines a fad as "a practice or interest followed for a time with exaggerated zeal." Fad diets often promise quick results with a short time commitment. Long-term success requires permanent changes in behavior, diet, and activity.
“If a client has come to me looking to lose 10 pounds, I would tell them to simply move. Move more, and more often. Walk or bike ride to class or work, even park further away from your location in the parking lot. Take the stairs or take a walk during lunch. You don’t have to spend hours every day in the gym sweating, but you do have to make a conscious effort to move more, and sit less. This works great because it doesn’t feel like work and you’re burning more and more calories throughout the day.” — Ajia Cherry, personal trainer and Founder at Functional Innovative Training
Prepackaged foods are not for everyone and typically not something to use forever. They can be very limiting and create the sense of being "on a diet." They will also get in the way of social events in which food is involved. Most people find that they only want to use this type of a diet for the short-term or for one or two meals per day. The other negative aspect of this diet is that the prepackaged foods contain the artificial sweeteners Sucaralose and Acesulfame K.
Useful goals should be (1) specific; (2) attainable (doable); and (3) forgiving (less than perfect). "Exercise more" is a great goal, but it's not specific. "Walk 5 miles every day" is specific and measurable, but is it doable if you're just starting out? "Walk 30 minutes every day" is more attainable, but what happens if you're held up at work one day and there's a thunderstorm during your walking time another day? "Walk 30 minutes, 5 days each week" is specific, doable, and forgiving. In short, a great goal!