Your Body Almanac

Keto or low-carb diet

Cutting bread, rice, sugar and often fruit to burn fat instead.

Cutting carbohydrates can help some people lose weight and lower blood sugar in the short term. Strict keto, though, removes many sources of fiber, potassium and magnesium, and can raise LDL cholesterol in some people. Most of the early side effects come from fluid and mineral shifts.

01

The first-week slump

In the first days, your body sheds stored water and the sodium and potassium that go with it. Headache, tiredness, dizziness, brain fog and leg cramps, sometimes called "keto flu", are common. Water and mineral-rich low-carb foods help. Avocado, leafy greens, nuts, seeds and fish are keto-friendly sources of potassium and magnesium.

SourcesShould you try the keto diet? (Harvard Health Publishing)Low-carb diet: Can it help you lose weight? (Mayo Clinic)
Drink water through the dayDailyKeep a water bottle within reach and sip through the day instead of waiting until you are thirsty. Eat potassium-rich foodsDailyFill up on beans, potatoes, squash, fruit and dairy to reach the recommended amount of potassium. Eat magnesium-rich foodsDailyWork a magnesium source into each meal. Many Americans fall short of the recommended amount.
02

Constipation from low fiber

Dropping grains, beans and most fruit removes much of your fiber. Constipation is one of the most common complaints. Low-carb vegetables, nuts, seeds and avocado help fill the gap.

SourcesConstipation (NIH NIDDK)How to get more fibre into your diet (NHS)
Hit a daily fiber targetDailyWork up to 25–35 grams of fiber a day from whole grains, beans, fruit, vegetables, nuts and seeds. Drink water through the dayDailyKeep a water bottle within reach and sip through the day instead of waiting until you are thirsty. Eat a range of colorful produceDailyGet at least five servings of vegetables and fruit a day, mixing greens, reds, oranges, citrus and beans.
03

Cholesterol and saturated fat

Diets heavy in butter, red and processed meat and cheese can raise LDL cholesterol in some people. Choosing fish, olive oil, nuts and avocado for fat, and checking your cholesterol, keeps track of it.

SourcesKetogenic diet — is the ultimate low-carb diet good for you? (Harvard Health Publishing)
Eat fish twice a weekWeeklyGet at least 8 ounces of seafood a week, favoring fatty fish that is low in mercury. Get a yearly checkupYearlySee your primary care provider for preventive care, the screenings and vaccines you are due for, and questions about your health.
04

Kidney stones

Very high animal protein, low fluid and low citrus intake are linked to kidney stones, and stones are a known side effect of long-term keto. Drinking enough water is the main defense.

SourcesEating, Diet, and Nutrition for Kidney Stones (NIH NIDDK)Should you try the keto diet? (Harvard Health Publishing)
Drink water through the dayDailyKeep a water bottle within reach and sip through the day instead of waiting until you are thirsty. Eat a range of colorful produceDailyGet at least five servings of vegetables and fruit a day, mixing greens, reds, oranges, citrus and beans.

When to see a professional

Talk to a doctor before starting keto if you take medicine for diabetes or blood pressure (doses may need to change quickly), or have kidney, liver, pancreas or gallbladder disease, or a history of an eating disorder. Get care for severe pain in your side or back, blood in your urine, or a racing heart.