The Keto Diet: Does it Really Work?

By Natalie Romito, RD, LD; updated by Amanda Garman, MS, RDN, LD

You’ve probably heard the hype about the keto diet. The high-fat, low-carb “ketogenic diet”, as it’s formally called, is a common weight diet. Why? One reason could be because the keto diet results are real, and it does work…technically.

The Keto diet works because when you restrict dietary carbs – your body’s main source of energy – your body breaks down stored fat and creates ketones to use for energy instead. However, calories still matter. If you overeat on protein and fat, and your total calories are beyond what your body is burning, you will still not see weight loss. High fat, high protein foods (the foundation of this diet) increase satiety, so typically total calorie intake is lower than what your body burns, and weight loss results.

The rapid weight loss people experience with their keto diet results initially is also partly due to loss of water weight – your body stores carbs with water, so when you use up your carb stores, you lose water weight. Most people simply don’t burn enough calories to lose more than about two pounds of fat per week, so keto diet results totaling more than that are likely due to losses in water weight.

Weight regain is extremely common on the keto diet, as most people cannot sustain this diet long term, and once carbs are reintroduced, people often see weight gain and diminished keto diet results.

Is the Keto Diet safe?

While eating a diet with high amounts of protein and heart-healthy fats and fewer carbs is generally safe, there are some concerns with following the keto diet, including:

• Low blood sugar levels, especially among people with diabetes who are taking medications.
  If you have diabetes and are set on following this diet, I would strongly encourage you to contact your physician to discuss how to adjust medications during the diet, as low blood sugar levels can be deadly.
• Increased insulin resistance.
  Insulin resistance occurs when fat builds up in the muscle. This prevents insulin from lowering blood sugar and results in high blood sugar levels.
• Increase risk of heart disease.
  High intake of saturated fats and high-fat meats can lead to increased cholesterol levels, which can increase risk of heart disease. Additionally, a low-carb diet has been associated with decreased antioxidant intake and increased oxidative stress. This may be associated with developing heart disease and diabetes.
• Nutrient deficiency risk.
  Eliminating or greatly restricting multiple entire food groups (fruits, whole grains, dairy, and limiting vegetables) puts a person at risk of developing a nutrient deficiency. This risk increases the longer the diet is followed. And yes, you could take a multivitamin, but most vitamins are best absorbed when consumed as food, rather than in a pill, and they don’t contain the same antioxidant benefit as whole foods. A low-carb diet is often low in fiber. Fiber is an important nutrient that helps regulate blood sugars, bowel movements, and cholesterol levels.
• Dangers for those with kidney disease.
  People with kidney disease would want to avoid this diet, as the excess protein that often comes along with this diet may progress kidney disease more rapidly.

The Keto flu

There’s one more thing to be aware of when starting the keto diet. The first couple of weeks can be filled with positive keto diet results that seem promising, but those first weeks can also be tough. That’s because your body is adjusting to a different fuel source, and this adjustment period may leave you with symptoms of what people are terming “the keto flu”.

These symptoms include:

• Tiredness, lethargy
• Feeling achy
• Mild headaches
• Cloudy, slow thinking
• Lightheadedness
• Some hunger
• Constipation

When you transition to the keto diet, your body is literally adjusting from being a carb-burning machine to a fat-burning machine. That adjustment can sometimes show itself through unpleasant sensations like those people refer to as the “keto flu,” although I want to be clear, the symptoms are in no way an actual flu-like illness, and they should subside once your body has adjusted to its new fuel source.

What should you eat on the Keto Diet?

If someone told me they were going to follow a keto diet, even if I advised against it, I would make the following recommendations for what to eat:

1. Get most of your carbs from non-starchy (lower carb) vegetables and whole food, unsaturated fat sources such as avocados, nuts, and seeds, and remember that most of the carb in these foods comes from fiber.
2. Choose a variety of meats, as different meats have different vitamins/mineral content. Choose fatty fish such as salmon and low fat meats such as skinless chicken/turkey, loin/tenderloin cuts of beef and pork, and lean or extra lean ground meat (10% fat or less).
3. If you have a history of high cholesterol, limit egg yolks, choosing mostly whites. Most people can eat the yolks without a big change to cholesterol, but others are very sensitive to the cholesterol in foods, so extra egg yolks often consumed on a keto diet can cause cholesterol levels to increase.
4. Limit cheese intake (1oz is a serving), or choose low-fat cheese rather than full-fat cheese to limit saturated fat intake.
5. Choose fats in the form of whole plant foods most often – avocados, olives, nuts, nut butters, and seeds. Cook in liquid oils if needed rather than solid oils (like butter, bacon or lard) to help maintain healthy cholesterol levels.
6. Take a multivitamin daily.
7. Allow yourself as much variety as possible within these food groups to avoid boredom and to get the most nutritional benefit from the foods you are choosing.
8. Remember that this is not a realistic lifestyle change for most people, so it is important to have a plan for transitioning off the diet.

Transition off the Keto Diet

If you decide to come off the keto diet, don’t make the transition cold turkey. Rather, I recommend transitioning off the diet by following these guidelines:

1. Reintroduce carbs gradually until you’re consuming at least 100-135 grams per day. You may need to increase to a higher level, depending on what would be a realistic amount of carb intake for you to maintain long-term.
2. Choose whole, unrefined carbs, such as whole grains, fruits, and vegetables.
3. Expect weight gain with the reintroduction of carbs, and know that at least part of the gain is likely due to retaining water as your body replenishes its stored carbs.

I recommend talking to your doctor before making any kind of major switch to a weight loss diet such as the keto diet. Ask your doctor or dietitian if the keto diet is safe for you, and how you can approach it in a way that’s healthy for your body, but also helps you to achieve the health results you want.