Low-Carb Diets Like Keto Can Help You Lose Weight Now, But May Harm You Later
Recent studies show that low-carb diets may increase your risk of dying at a younger age. Plant-based diets may be better.
Many people turn to low-carb, high-fat diets to lose weight and improve their metabolic health.
But recent studies suggest that staying on these diets for years or decades may increase your risk of earlier death.
The researchers point to the importance of eating more plant-based whole foods, including fats and proteins as well as a moderate amount of carbohydrates.
One of these studies, published last month in The Lancet, looked at the eating patterns of more than 15,000 middle-aged Americans, following them for an average of 25 years.
The researchers combined their results with seven other similar studies from around the world — what’s known as a meta-analysis.
They concluded that people who followed a low-carb diet over the course of the study had an increased risk of dying in midlife.
High-carb diets also increased the mortality risk, but not as much.
The lowest mortality was among people who obtained 50 to 55 percent of their energy from carbohydrates — the carb “sweet spot.”
Another study, presented at a European Society of Cardiology meeting last month, showed similar results.
This study found that people who ate the fewest carbohydrates — compared to those who ate the most — had a higher risk of death from any cause, as well as from coronary heart disease, cerebrovascular disease, and cancer.
Dr. Michael Chan, an interventional cardiologist with St. Joseph Hospital in Orange, California, said “the studies were both well-done, and certainly raise some interesting questions about whether there are long-term risks with a low-carb diet.”
Chan was not involved in either of the studies.
People on the keto diet fall far below the carb sweet spot.
They usually get less than 10 percent of their calories from carbohydrates, with 70 to 80 percent coming from fat, and the rest from protein.
Some research has found that people on a low-carb diet lose weight more quickly than those on a low-fat diet. But other studies haven’t found much difference between the two in terms of weight loss.
That suggests that the best way to lose weight and keep it off is to find a healthy diet that you can sustain.
The big question here, though, is whether it’s healthy to stay on a low-carb diet for decades.
Dr. Ethan Weiss, a cardiologist researcher at the University of California, San Francisco, doesn’t think nutritional epidemiology studies, like the one in The Lancet, can answer that question.
One reason is that both of the new studies are observational, not randomized clinical trials.
Chan raised the same concern, saying observational studies “can show an association, but not necessarily that the low-carb diet caused increased mortality.”
People in the study also only reported what they ate twice over 25 years — trying to remember what they ate rather than writing it down in real time.
“We all have an incredibly difficult time recalling what we eat,” said Weiss, adding that food recall surveys are “at best, 50 percent accurate.”
Weiss is an advisor for Virta Health, a company that promotes the use of the keto diet for people with diabetes.
But he’s not the only researcher who questions the usefulness of nutritional epidemiological studies.
Weiss would like to see more randomized controlled trials that compare two diets — such as keto vs. a whole-food, moderate-carb diet.
Chan agrees that more research is needed before we can “draw firm conclusions.”
It may be years, though, before we have the kind of “hard data” that Weiss is looking for.
In the meantime, he has “no problem recommending the keto diet for my patients, friends, family,” he said. “I think it’s a really effective tool for weight loss. Is it the only effective tool for weight loss? Of course not, but I think it’s really powerful.”
If low-carb fits your health goals, it’s best to do it in the healthiest way.
Chan said the American Heart Association recommendations are a good place to start — eat a variety of vegetables and fruits and fiber-rich whole grains, avoid trans and saturated fats, cut back on added sugars in foods and beverages, and use portion control.
Kristin Kirkpatrick, MS, RDN, lead dietitian and manager of Wellness Nutrition Services at the Cleveland Clinic Wellness Institute in Ohio, said the key thing with low-carb diets is what you replace the carbohydrates with.
In the Lancet study, researchers found that people on a low-carb diet who consumed mainly animal-based protein and fats had a higher mortality risk than people who turned to plant-based sources.
They write in the paper that when you cut back on carbohydrates, you can lose many of the nutrients that plants provide, such as branched-chain amino acids, fatty acids, dietary fiber, phytochemicals, vitamins, and minerals.
Chan said this finding “adds support to many of the current recommendations to incorporate more vegetables and plant-based foods into our diets.”
But he added that even here, more research is needed to confirm the findings.
Other studies, though, support the role of plant-based foods in keeping us healthy.
“There are clear studies showing that getting adequate fruits and vegetables in the diet can help in the long run to reduce the risk of chronic disease, inflammation, and cancer,” said Kirkpatrick.
So whatever your diet, eat plenty of vegetables.
For people on a low-carb diet, Kirkpatrick has a few recommendations:
- Stick with non-starchy vegetables such as spinach, asparagus, cauliflower, and broccoli to avoid extra carbohydrates.
- Eat as many plant-based proteins as possible, although this can be challenging on a keto diet because beans are high in carbohydrates.
- If you eat meat, aim for more skinless poultry and fish, which are lower in saturated fats.
- Eat more monounsaturated — “healthy” — fats such as those from nuts, seeds, and avocado.
- If you have some carb allowance left over, eat small amounts of berries, which are rich in vitamins and antioxidants.
- Avoid low-quality foods with added sugars or refined white flours and other non-whole grains.
Weiss, who does a modified keto diet, has had “good results on it, from the standpoint of weight loss.”
He does eat fatty meat from time to time, but he also eats more of the “healthy fats” that Kirkpatrick mentioned.
The restrictive nature of the keto diet, though, has shifted how he thinks about food.
“It’s very hard to maintain a ketogenic diet and eat food that you buy at a restaurant or somewhere outside your house,” said Weiss.
Instead of getting a burrito at a food truck or going to Subway for lunch, he now prepares about 90 percent of his own meals at home.
This is an eating pattern that many other diets call for, from whole foods to anti-inflammatory to vegan.
“I eat a ton of vegetables, and I’ll put salmon or chicken on a salad, with lots of nuts, cheese, avocado, and olive oil,” said Weiss. “Basically, now I know what I’m putting in my body — and it’s all fresh whole food.”
Diet, though, is only one component of healthy living.
“It’s always helpful for patients to focus on ways to improve their diet and exercise habits,” said Chan. “I always emphasize these two as foundational components to good health.”
And “if you are a smoker… quit,” he added.
Low-carb diets can help you lose weight and improve your metabolic health.
But recent studies suggest that, long-term, they may increase your risk of dying younger.
To minimize the potential harms of a low-carb diet, eat high-quality foods, including as many low-starch vegetables and nutrient-dense fruits as your plan allows.