It's Based on Natural Unprocessed Food
First of all, a healthy diet program involves eating real wholesome food, not synthetic meal replacements. This means fruits, vegetables, whole grains, nuts, seeds, dairy (preferably organic) and other nutritionally-rich, unprocessed foods. You can lose weight on any kind of reduced-calorie eating plan, but if you want to stay healthy too, it's vital to include plenty of high quality fresh foods. So avoid any diet plan that would have you living on junky processed food or meal replacement drinks - they just don't cut in over the long term.
No Diet Pills
Diet pills can sometimes help people to lose weight more quickly, but their long term effects on the body are unknown. Putting your health at risk for short term weight loss is not a good idea, especially if you don't make any changes in your eating and lifestyle habits. With a healthy diet and moderate exercise, there's simply no need to pop pills to lose weight, and a healthy weight loss program won't require their use.
It's possible to lose weight without exercising, but for long term health, taking some exercise is a must. Exercise can help to prevent chronic health problems, and also provides an immediate boost to your mood and energy levels. In addition, exercise helps with weight loss by burning calories during your workout, by increasing your metabolic rate for some time afterwards, and by building lean muscle tissue, which is more metabolically active than fat - meaning that you burn more calories even when you're at rest. So for optimal health, make sure your weight loss program includes at least twenty minutes of exercise three or four days a week.
Eat Enough, Often Enough
It's vital to give your body enough food when you're attempting to lose weight. It can be tempting to crash diet or skip meals, but this puts your body under stress, decreases your energy levels, and makes you more likely to overeat. If under-eating becomes a habit, you're also at risk of malnutrition. As well as having negative health effects, skipping meals won't really help with weight loss, since your body will slow its metabolic rate, making fat loss more difficult, and making it likely that you'll regain even more weight than you lost when you start eating normally again. So to lose weight healthily, eat at least three meals a day (many people find that four or five smaller meals works better), and never be tempted to skip a meal.
Make Permanent Changes
Any diet plan that relies on short term, faddy methods such as cutting out whole food groups, taking diet pills or drastically reducing calories is not going to promote either permanent weight loss, or long term health. Most people find that such plans are impossible to stick with for long for long, as the body eventually rebels, forcing you to eat more to provide what it needs. Any healthy weight loss plan will emphasise how important it is to make permanent changes in your eating habits, and to eat adequate but not excessive quantities of healthy, unprocessed, nutritionally-dense foods. If you're used to chronically overeating, or living on junk foods, this can be a challenging change to make, but it's doable, with time and patience. And it's worth the effort, because once you've established healthy new habits, you'll keep the weight off, and be free from the yoyo cycle of weight gain and loss for ever - and you'll feel great too.
So if you want to lose weight, keep it off, and be vibrantly healthy, look for a health-based weight loss plan that avoids short term gimmicks and instead focuses on doing what's best for your body.