Since I’ve lost 10+ pounds multiple times, I’m something of an expert in the practice. Having gained 10+ pounds more than once (or twice or thrice), I know how to do this too.

In the generosity of the holiday season, I’ll give away my secret: For the former, decrease the number of calories consumed and increase the number of calories burned. The higher those numbers are, along with the amount of time this lasts, will determine the amount of weight loss. To do the latter, reverse the process.

The only other factor is a person’s metabolism. Everything else is fluff. There are tips that can help, such as drinking water to feel full, or exercising with a partner because one is less likely to stand up a friend than to blow off the gym out of laziness. And 100 calories from a banana will give you more lasting energy and feeling of fullness than 100 calories from a cookie. But everything must still fall under the calorie reduction umbrella.

But the diet industry brings in $20 billion a year and the adult obesity rate has fattened to 30 percent, so there will always be someone looking to create an even slicker snake oil.

One can eat like a bird in metaphorical sense, using the Hollywood 48-Hour Miracle Diet or similar starvation method. Birds consume a tremendous amount of food in relation to their body weight, so one can eat like a bird in the more literal sense by using the original Atkins diet. One can eat like a rabbit (raw food diet), eat like a prehistoric hunter-gatherer (Paleolithic diet), or eat like a Miami cardiologist who has cashed in big on selling the concept of calorie reduction (South Beach Diet).

Other fad diets focus on lemonade, the Bible, food separation, and the dieter’s blood type. These diets will work if the number of calories consumed goes down enough and the amount of calories burned goes up enough. There are no magic pills, potions, or diets deciphered from papyrus left inside a mummy’s casket.

Fad diets are fueled by advertising campaigns and anecdotes, rather than random, double blind, reproducible studies. Most will not usually be unhealthy, except in cases of extreme calorie reduction. However, high protein-low carbohydrate diets force the body into ketosis for prolonged periods and can harm the bones, heart, liver, and kidneys. Some go beyond dieting and claim foods will cure diseases, which can be potentially fatal advice.

The industry displays remarkable flexibility in coming up with new twists on a centuries-old idea. Throwing in a misused scientific term or two is one trick. For instance the alkaline diet’s stated goal is to alter the dieter’s pH level, purportedly leading to more weight loss. But food consumption will never substantially impact the pH level since normal bodily functions keep it constant. Food in the stomach will be acidic and the food that has moved on to the intestines will be alkaline. And even if this did work, the diet would still require calorie reduction to cause weight loss.

Sometimes legitimate diets are born from medical needs that are necessary for some people. The gluten-free diet is one example. However, some persons twist this and declare that gluten or whatever else is bad for everyone, and start selling products to promote that diet.

The keys to good health are ingesting fruits, vegetables, grains, legumes, nuts, water, and protein, while engaging in exercise that boosts flexibility, muscle, and cardiovascular fitness. Adequate sleep, medical checkups, and sparse use of sweets and alcohol are other big factors.

Most fad diets say to incorporate these habits into their program. But doing all this makes their diet superfluous. If you do these things and replace the reticulated frog beetle diet with listening to viola concertos, you’ll get the same result.