For many people, this "season of wonder" includes wondering if you can cheat on a healthy diet. How much can you indulge in rich, salty, or sugary holiday cuisine without risking weight gain, heart and blood pressure problems, or high blood sugar?
"Some people are more sensitive than others to salt, saturated fat, or added sugars. We sometimes see diet affecting blood pressure or cholesterol in as little as a few weeks after people splurge," says registered dietitian Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital.
That makes dietary cheating a bit risky. But for generally healthy people, McManus says there is a formula that allows you to bend the rules this holiday season and beyond.
First, the healthy guidelines
Ideally you should always follow a healthy eating plan, such as a Mediterranean-style diet. In addition, you need to limit the following.
Added sugars. Eating too much sugar can cause repeated blood sugar spikes and increase your risk for diabetes. Limit intake to no more than 24 grams per day for women and 36 grams for men.
Salt. In some people, consuming too much salt can increase blood pressure. Healthy people should limit intake to 2,300 milligrams (mg) per day.
Saturated fat. Eating too much of this type of fat — found in red meat and full-fat dairy products — can increase "bad" LDL cholesterol and raise your risk for heart disease. McManus advises limiting saturated fat to 7% of your daily calories. To figure out how many grams of saturated fat that would be, take 7% of your daily calories and divide it by nine (one gram of fat has 9 calories). For example, if you're eating 1,500 calories a day: .07 times 1,500 equals 105; 105 divided by 9 is about 12 grams of saturated fat.
What about calories?
Daily calorie needs depend on many factors, including your age, activity level, body composition, overall health, and weight goals (such as weight loss).
If you're a healthy person who exercises 30 minutes per day, you can estimate how many daily calories you need to maintain your current weight by multiplying your weight (in pounds) by 15.
For example, if you weigh 130 pounds, multiply 130 by 15. The answer — 1,950 — is the number of calories you need per day to stay at 130 pounds. Eating more could lead to weight gain; eating less could lead to weight loss.
Bending the rules
While a good diet is crucial for health, bending the rules on occasion probably won't hurt. A tip you can try is the 90-10 rule. "Eat a healthy diet 90% of the time and splurge 10% of the time," McManus says. "Eating three meals a day for a week means 21 total meals: avoid splurging for more than two of those meals."
What about doing a 90–10 plan every day during the holidays, devoting 10% of your daily calories to unhealthy holiday foods? That's probably more likely to lead to bad habits. "If you occasionally go slightly over the daily guidelines for calories, salt, added sugar, and saturated fat intake, it's probably not going to be a problem," McManus says. "But making every meal a little unhealthy, by design — that's likely to cause problems."
Knowing that you can cheat a little might tempt you to push the 90-10 rule beyond its limits. For example:
You might overdo a cheat meal. We know for sure that a regular diet that's unhealthy can, over time, increase your long-term risk of developing heart disease. But it may also be true that a big, unhealthy meal can cause immediate risks. Let's say you binge on a juicy steak, mashed potatoes, and a hot fudge sundae. That rich meal contains 47 grams of saturated fat, 32 grams of mostly added sugars, 1,330 calories, 70 grams of carbohydrates, and 2,555 mg of sodium.
Some small studies suggest eating a heavy meal increases the risk for a heart attack. "Theoretically, a large, unhealthy meal does lead to various biochemical changes in the body, such as increases in triglyceride levels, which could contribute to an elevated risk for heart attack in the hours following the meal," says Dr. Deepak L. Bhatt, a cardiologist and the editor in chief of the Harvard Heart Letter.
You gain weight and keep it on. Maybe you'll exceed the dietary guidelines for the entire holiday season and tell yourself you'll compensate for it in January and February. Unfortunately, studies of what actually happens in the post-holiday period find that many people weigh more in March than before the holidays: January and February didn't fully correct for the holiday splurging. Perhaps you get used to indulging and then can't break that habit. Perhaps once you gain weight, your body resets your metabolism to a higher weight, so you get hungry more easily.
"Unless you're putting a lot of effort into maintaining weight loss, you can return to the previous baseline weight," McManus explains. "Biology isn't on our side, and old behaviors are still there. We may slide back into our previous ways, and calories will go up and exercise will go down. So weight drifts back up."
What you can do
Try to follow a healthy diet on most days, and allow yourself the pleasure of occasionally indulging.
"For the holiday season, you may want to enjoy a few particular dishes, meals, or events," McManus suggests. "Plan ahead for that. But also plan how you'll be eating when you're not overindulging."
Carry that idea through to January and then each month after that. Don't bargain with yourself; try to maintain an even style of healthy eating, with occasional cheating on your diet. You'll wind up feeling satisfied that you get to enjoy the foods you love, and you may have more success maintaining your weight goals.