The right way to count calories, according to weight loss experts

Last week at Vox, we published a feature that pooled advice from 20 leading researchers, doctors, and dietitians on how to lose weight and keep it off.

One of the key take-home messages was that science — and clinical experience — have demonstrated that tracking what you eat in a food diary is associated with losing more weight in the long term. One study showed that food diarizers lost twice the amount of those who didn't track.

Counting calories helps people to be more mindful about what they're eating, when they are eating too much, and where they might be going wrong, they said.

Almost as soon as I published the piece, however, I heard from readers who thought that tracking their food intake was much easier said than done.

Or, as one coworker put it: "How do I log the three bites of chocolate banana cake that was on the Vox kitchen counter this morning?"

Read more: Surprisingly simple tips from 20 experts about how to lose weight and keep it off and Everything you wanted to know about weight loss and obesity

Another noted that she often starts tracking, but then gives up when she eats out; calculating a restaurant meal is too difficult.

I went back to the experts to see what advice they had about how best to track. Here's a quick summary of what they told me:

1) Stop trying to be perfect

Calorie counting, while important, does not always have to be a perfect science.

"I am not crazy exact about counting calories," said Dr. Arya Sharma, director of the Canadian Obesity Network. "I recommend caloric awareness. You just need to be somewhere in the ballpark, it's nothing to obsess about."

On the face of it, this seemed to contradict the message that knowing exactly what's going into your body is extremely important when it comes to weight loss and maintenance.

But the doctors were trying to say that, realistically, no one is going to be able to tally perfectly the nutrition content of every bite, every day. Keeping some kind of food diary — even if you don't get the calorie total exactly right — helps people to be more careful about what they're consuming. Imperfect tracking is better than none at all. When done over a long period, it might even change how you eat.

"Just guessing maintains thoughtfulness and reminds a person of all of the changes they’re trying to make," said obesity physician and Diet Fix author Dr. Yoni Freedhoff.

"A food diary is simply a source of information to help inform your decisions"
As I wrote in last week's feature, I once had to lose nearly 30 pounds and tracking helped give me a good sense of what I was eating. I'm by no means perfect, but I logged for long enough to know the nutrition makeup of most of the foods I regularly eat, so now I'm often tracking in my head.

Whenever I feel I'm not being careful enough, I use an app for an extra nudge (more on that later). I don't aim for perfection or fret when I miss a meal or even a day. The mere act of tracking helps me stay focused and better understand where my calories are coming from.

As Dr. Freedhoff has said, tracking shouldn't be punitive or judgmental: "A food diary is simply a source of information to help inform your decisions, as well as an incredibly powerful habit-building tool."

How many calories in three bites of chocolate cake? (Photo by Tiziana Fabi/AFP/Getty Images)

2) When dining out, assume the worst and use your hand to estimate portion sizes

Experts do have some tips for how to estimate in situations where calorie counts aren't available. The first: assume the worst.

"When eating out, it's a good bet, even when choosing healthier options, that you are going to eat more calories than you would at home," said Katherine Zeratsky, a registered dietician at the Mayo Clinic.

The gurus all suggested over-estimating your calorie intake whenever you have a meal outside of the house.

Add 40 percent to non-posted calorie counts for meals at restaurants
Dr. Freedhoff recommended adding 40 percent to non-posted calorie counts for meals at restaurants, and 20 percent to posted information (since studies have shown that restaurants often undervalue the actual calorie content of their foods).

Zeratsky had some other helpful advice about counting: a portion of lean meat or protein the size of a woman's palm is worth about 200 calories. But, again, most restaurant portions are much larger, and probably include at least 120 calories (or a tablespoon) of fat for cooking.

A cup of starch — such as a pasta or potatoes — would be about the size of a woman's fist. This would include 180 to 220 calories, depending on sauces, fats, or other ingredients used during cooking.

Vegetables are very low in calories, but again — Zeratsky said she'd add a minimum of 120 calories for cooking fat (unless the greens were steamed).

As for desserts, such as those found in the Vox kitchen: Zeratsky said it's safe to assume they contain about 25 to 50 calories per one tablespoon. "Those three bites of decadent dessert," she said, "could be 100 to 150 calories."

(Photo by Frank Bienewald/LightRocket)

3) Use an app to track

"One of the mobile apps like Lose It can help," Dr. Lawrence Cheskin, director of the Johns Hopkins Weight Management Center, suggested.

The other weight loss gurus noted that apps have made tracking so much easier today than in the past, when calorie books and old-fashioned pen and paper tallying were the norm.

I have found MyFitnessPal to be very useful: you can set reminders for when you've forgotten to log a meal, and it saves the foods you eat frequently so once you've been using it for a while, it only takes a few minutes to log each day.

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