Although what you observe when you’re out and about suggests otherwise, people are not fated to be fat.

As Alanna Collen notes in “10% Human” (Harper, 2015), “sixty years ago almost everyone was thin, despite having broadly the same gene variants as the human population today.” The book suggests the overuse of antibiotics and the pervasiveness of the Western diet, as well as a few common medical and grooming practices have altered our gut microbiota enough to make that alteration a major factor in the obesity “pandemic.”

Moreover, that replacing good gut bacteria with bad bacteria has also dramatically increased the rates of “twenty-first-century sicknesses,” illnesses relatively rare before the discovery of penicillin and the mass production of highly processed foods. Illnesses such as allergies, eczema, asthma, diabetes, multiple sclerosis, celiac disease, lupus, rheumatoid arthritis, Crohn’s disease, ulcerative colitis, attention-deficit disorder, obsessive-compulsive disorder, Tourette’s syndrome, and depression.

Read the book and you may very well come to believe as Hippocrates did: “[D]eath sits in the bowels.” For sure, you’ll never look at bottle feeding a baby, the meat you eat - or even organic vegetables - in the same way again.

But this column is not a book review. “10% Human” is only cited because it asserts something I’ve said time and time again.

That, despite making amazing inroads in understanding how the foods we eat affect our health, our current knowledge of diet is “distressingly incomplete.”

The rate at which dietary advice changes attests to this. Take, for instance, all the flip-flopping we’ve done on dietary fat.

In the 1960s, one specific type, saturated fat, became the bogeyman, so most doctors advised replacing butter with margarine, which lead to a far bigger bugaboo. Margarine at that time was loaded with trans fat, which was later shown to be a far greater cause of heart disease than saturated fat.

Our fear of saturated fat morphed into the fat-free craze that lasted nearly two decades - until consuming carbohydrates became the new dietary devil. Now consuming ample amounts of all types of fat as part of low-carb diet became de rigueur.

The no-carb craze lasted nearly as long as the fat-free one.

Since then, the flip-flopping about dietary fat has continued, confusing dieters to no end and causing many to question the effectiveness of dieting - especially when some studies suggest of any type is futile.

Probably the best known of these was published in the May 2016 issue of Obesity and revisited the 2010-season contestants of “The Biggest Loser.” The 14 started the television competition weighing an average of 328 pounds.

By its conclusion, they had lost an average of 128 pounds.

Six years later, however, the typical contestant had regained 90 pounds. Only one of the 14 weighed the same as when the show closed.

Before the competition started, contestants burned on average 2,607 calories per day. By its end, basal metabolic rate dropped on average to about 2,000 calories per day.

Such a change is called metabolic adaptation and is expected.

What wasn’t expected is that the BMRs kept going down. They should’ve rebounded as weight was regained.

The average BMR six years later, however, was 1,900 calories per day.

That’s an overall decrease of more than 27 percent, one that could make even Jenny Craig herself fearful that the return of lost weight is indeed inevitable. Because of my fervent belief in nutrient partitioning, though, I don’t share that concern.

My belief is bolstered by a 2020 study published in the American Journal of Clinical Nutrition that called metabolic adaptation an “illusion.”

In this study, 71 middle-aged obese individuals were placed on a 1000-calorie-per-day diet for eight weeks, which produced an average weight loss just under 31 pounds. After a nine-month weight loss maintenance program that followed a one-month adaptation period, the subjects had regained on average almost nine pounds.

While this outcome would seem to support the Biggest Loser study, another one doesn’t. For subjects who remained in the program to the end, the metabolic adaptation that occurred as a result of the dieting “disappeared.”

Their new energy-balance mark was only seven calories less than expected.

So whether you’d like to drop five pounds of fat or 50, here’s my dieting plan for you. Use whatever diet you believe will work for you - to get started.

Lose as much weight as you can, but don’t sweat it if you fall short of your goal. The maintenance plan you will follow, where you’ll practice nutrient partitioning, will not only keep you from regaining the lost weight but also allow you to lose a few pounds more if you choose.

You’ll eat smaller meals five to six times a day and - here’s the key - most of the calories will come from proteins and complex carbs loaded with fiber. Doing so will cause a different type of metabolic adaptation to take place.

You’ll burn more calories than someone else of the same weight on a standard Western diet because the cals you’re consuming won’t burn as easily or efficiently as simple carbs and fats - nor will they be as likely to be stored as body fat.