August 29

A friend of mine is trying to lose weight and wanted to check whether her strategies were sound. She said she counts every calorie, avoids nuts because of the high fat content and snacks only on sugary (but fat-free!) foods. Was she on track?

If that conversation took place in 1993, she’d get kudos for her nutrition knowledge. But those bits of wisdom are badly outdated. Nutritional science changes quickly, and knowledge that was gleaned from a 25-year-old nutrition textbook needs to be refreshed. Here’s how nutrition information has changed over the years and why it’s important to keep up.

All fat is bad: I remember the on-campus breakfast I ate most often in 1994: a huge New York-style bagel with nothing on it. We all believed that “fat makes you fat,” so butter, cream cheese and peanut butter were off-limits. Fat-free foods were deemed better for health, so nuts, seeds and avocado were frowned upon. A low-fat, high-carb diet was the recommended approach for weight control and good cardiovascular health.

Check your menu. If you are still eating pasta without olive oil or bread without peanut butter, you’re doing yourself a disservice. Fat should not be feared. Certain fats, especially from nuts, seeds, olive oil, fish and avocado, are beneficial for heart health and weight control, and can help reduce the risk of developing Type 2 diabetes. They should be enjoyed as part of the daily diet.

Fructose (fruit sugar) is better for diabetics: My nutrition textbook from 1995 says that “fructose does not cause problems of high blood sugar for people with diabetes.” Fructose naturally occurs in fruit, and it’s fine in small doses. But in the 1990s, fructose was heavily used as a sweetener for processed foods because we thought it was healthier than white sugar. Remember Frookies, the fructose-sweetened cookies for people with diabetes? Yikes.

It turns out that excessive consumption of fructose — mostly as high-fructose corn syrup — has been linked to insulin resistance and Type 2 diabetes, so it’s not good for diabetics after all. Too much fructose is also associated with metabolic syndrome, obesity and cardiovascular disease. Fructose from fruit is fine, but high consumption of fructose in the form of sweeteners is not recommended — whether you have diabetes or not.

All calories are equal: I distinctly remember my nutrition professor saying, “It doesn’t matter if you eat 300 calories from apples or from chocolate — a calorie is a calorie.” In the mid-’90s, calories were all treated the same, no matter the source.

That was dietetic tunnel vision. We now recognize that calories from soda, candy and other treats deliver sugar but offer no vitamins, minerals, fiber or protein. That’s different than calories from vegetables, legumes or fish, which provide nutrients in every bite. If you still count calories but don’t consider much else, consider making an appointment with a dietitian to learn why nutrient-dense foods are a better option.

Sugar just causes cavities: My dorm room was stocked with Snackwell’s cookies, gummy bears and Snapple — all of my fat-free (and guilt-free!) pleasures. These fat-free foods are loaded with sugar. That didn’t seem to be a problem, because I was taught that sugar causes dental cavities but is benign otherwise. I brushed twice daily, so no harm done, right?

Fast-forward to 2017, and a new story emerges. Recent studies link excess sugar consumption — especially from sweetened beverages — to an increased risk of obesity, Type 2 diabetes, dementia and heart disease. Sugar is not as blameless as we once thought and should be limited. The American Heart Association recommends no more than six teaspoons of added sugar per day for women and nine teaspoons for men. One 16 fluid ounce Snapple has 10 teaspoons.

Calories in, calories out: Weight loss was explained very simply in nutrition school: You’ll lose weight by cutting calories from food and increasing calories burned through exercise. That’s it — just eat less and move more. Obesity was blamed on laziness and overconsumption.