The song is so well-known that even some youngsters who have nothing but rap on their play lists will know James Taylor’s soft-rock classic from 1970, “Fire and Rain.” What isn’t nearly so well-known is how quickly Taylor composed the lyrics.

Instead of needing days or weeks to turn his initial idea into a finished product, Taylor did so in a matter of minutes.

While I’ve never had a column come as easily, something similar did happen to me nearly 34 years ago. In the Q-and-A session that concluded the health and fitness course I was teaching, a woman asked why the diet that had produced a 20-pound weight loss for her girlfriend only dropped five pounds from her frame — even though they began the diet at the same time at nearly the same weight, ate the same meals, and exercised every day together.

My answer was effortless and unexpected and gave me a strange sensation. It was as if I were listening to the words spoken rather than speaking them. I heard myself likening the uniqueness of snowflakes to the systems in our bodies that determine whether calories get used as energy, stored as fat, or burned up in the digestive process.

Before I knew it, I was calling my explanation “The Snowflake Theory of Dieting.” I heard myself urging the class not to blindly follow any diet but to continually experiment, assess the results, and create a personalized diet.

I don’t remember if the class was impressed or not, but I do know that this advice went against what the typical nutritionist was suggesting. At that time, weight loss was seen as nothing more than a math equation: create a 3500-caloric deficit — preferably by both exercising more and eating less — and the loss of one pound is inevitable.

Subsequent studies have clearly shown that is not always so.We now recognize that the composition of the calories consumed — the percentage of protein, fat, simple and complex carbohydrates in the meal — is as important as the number of them.

We now know the hormones your body creates in response to the meal affects how it is digested, which in turn stimulates or stymies weight loss. We now know that other factors influence this hormone secretion, such as the amount and quality of sleep you get and the ratio of helpful to harmful bacteria in your gut.

Yet none of this was known the day I heard myself waxing poetic about the snowflakes and the need for personalized diets — which is why it’s so satisfying that my 34-year-old theory is now the new theory about dieting.

The need for you to create a personalized diet recently received strong support when the initial results of a study on twins’ responses to similar foods were presented at the American Society of Nutrition conference in Baltimore, Maryland and then at the American Diabetes Association conference in San Francisco, California. Researchers at King’s College in London, England and Massachusetts General Hospital in Boston, Massachusetts in conjunction with ZOE, a nutritional science company, found that more often than not identical twins had very different glucose responses to the same meals, regardless if the meal was high in carbs, low in carbs, or typical fast food fare.

Different glucose responses means different amounts of secreted insulin, the hormone most responsible for whether the broken down carbs become immediate energy, stored energy, or stored fat.

Moreover, the research revealed that a meal’s protein, carbs, fat, and fiber content accounted for less than 40 percent of the difference between the twins’ and all subjects’ biological responses to it. In other words, the individual differences in genetics, people’s metabolism, gut bacteria, times for meals, and degree of physical activity are just as important as the nutritional content of the food — and additional proof that the phrase “a calorie is a calorie is a calorie” should never be uttered again.

Tim Spector, a professor of genetic epidemiology at King’s College who led the study and is also the scientific founder of ZOE, explained for Medical News Today what’s occurring in the field of nutrition: “[T]here’s a real shift happening. People are finally starting to reject the notion that if everyone just follows the general guidelines (five servings of vegetables, counting calories, reducing fat) they’ll be healthy forever . . . that it’s not all determined by our genes or the nutrient composition of the meal.”

In short, Spector’s study of twins does far more than vindicate me; it offers a next step to all those who have failed to lose weight by following a fad diet. My only fear is that the majority of dieters will continue to follow fad diets because it’s easier than doing the planning, constant experimentation and appraisal, and critical thinking that personalized dieting requires.