Health often seems like a numbers game. What’s your blood-sugar level? How many calories are you eating? The problem is that sometimes we count and obsess over numbers that don’t matter very much or ignore numbers that do matter. Here, 20 medical experts weigh in on what matters and what doesn’t.

These matter most

Half your plate

Dietitians recommend that clients simplify food decisions by using a plate model, where you choose the right proportions of each food. That means filling half your plate with vegetables and some fruit; one quarter with protein-rich foods such as fish, poultry or beans; and a quarter with whole grains.

25 to 35 grams

That’s how much fiber a day we need for optimal health, but most Americans get just 16 grams per day. Getting enough fiber helps lower cholesterol and blood sugar levels, prevents certain cancers, eases constipation and keeps you feeling full for longer. Get more fiber from vegetables, fruit, beans, nuts, seeds and whole grains.

7 to 8 hours

Are you getting that much sleep every night? Lack of sleep has short-term consequences, such as poor judgment, increased risk of accidents, bad moods and less ability to retain information. Poor sleep over the long term has been linked to an increased risk of obesity, Type 2 diabetes and heart disease. So, power down your devices and get some rest.

150 minutes

That’s the recommendation for how much physical activity you should get each week. This level of activity helps combat heart disease, stroke, Type 2 diabetes, obesity, dementia and cancer.

100 mg/dl

Your doctor can test your fasting plasma glucose level to check for Type 2 diabetes. Lifestyle changes can prevent developing the disease or help reverse the diagnosis — but first you need to know your number. A diagnosis of pre-diabetes is 100 to 125 mg/dl, and a diagnosis of diabetes is 126 mg/dl or higher.

120 / 80 mmHg

High blood pressure is known as the silent killer. Left untreated, it is a risk factor for having a heart attack or a stroke. That’s why you need to get your blood pressure checked. Normal blood pressure is 120 /80 mmHg (millimeters of mercury) or less. Elevated is 121 to 129 over 80 and high is 130 to 139 over 80 to 89.

don’t matter very much

Size 8

Too many people have a diet goal to be a specific size, but the numbers on clothes are inconsistent and arbitrary. Focus on how you feel, not the number on the clothing tag.

50 years old

Or 86. Or 31, 75 or 27. Age is just a number. You are never too young to need to take care of yourself, or too old to start an exercise program or change what you eat. A healthy lifestyle is important at every age.

1,800 calories

Or whatever number you choose. You don’t need to count every calorie you eat. It’s often flawed, and it doesn’t help you choose nutrient-dense foods, such as choosing 100 calories of fries over 100 calories of broccoli. It oversimplifies eating into one silly number.

40-30-30

Or any other ratio of macronutrients, the umbrella term for carbs, protein and fat. Keeping track of macros is a popular diet, but some dietitians warn that it’s difficult to know the precise macro content of every food you eat.

Below 25

The body mass index (BMI) is a clinical tool that groups people in categories of normal weight, overweight or obese depending on their height and weight. But BMI doesn’t take age, gender or bone structure into account, and athletes are often classified as overweight because BMI doesn’t distinguish between muscle and fat. So, don’t rely on this number as your primary measure of health.