Many eating styles can support metabolic health, but specific diets present different benefits and challenges for maintaining balanced blood sugar. Whether you follow a vegetarian, keto, or Mediterranean diet, you can optimize your eating plan for metabolic health by following three guiding principles. Here’s how to do it.
3 Guiding Principles for Metabolic Health
Instead of debating the philosophy of one way of eating over another or worrying about whether specific foods are “good” or “bad,” ask these three questions about your diet:
1. Is it rich in nutrients?
Your cells rely on various micro and macronutrients in different foods, like the magnesium in pumpkin seeds and the omega-3 fatty acids in salmon. These organic compounds are the building blocks of the systems that enable our bodies to function correctly. If the food you eat lacks these nutrients, your metabolic health begins to decline. According to a 2018 review, micronutrient deficiencies may play a significant role in the development of metabolic diseases such as diabetes, hypertension, obesity, dyslipidemia, and other cardio-metabolic and neurodegenerative diseases.
2. Is it minimally processed?
Ultra-processed foods lack the micronutrients your body needs to function. They often contain the worst ingredients for metabolic health, like refined flour, sugar, and refined seed oils, as well as chemical additives (some of which are banned in other countries). Numerous studies have linked highly processed foods to poor metabolic health. For example, a meta-analysis of 23 studies showed that the highest levels of ultra-processed food intake increased a person’s risk of being overweight or obese by 39 percent and raised the risk of developing metabolic syndrome by 79 percent.
3. Is it low in sugar?
The negative effect of excess sugar on metabolic health is well-established. Consuming added sugars can contribute to metabolic disease by dysregulating lipid and carbohydrate metabolism and increasing body fat, which both increase your risk for metabolic disease. Added sugar consumption can also contribute to high glycemic variability (think: blood sugar spikes and crashes), which has been linked to brain fog, fatigue, and insulin resistance. A US Department of Agriculture study showed that in 2017-18, American adults consumed an average of 17 teaspoons of added sugar per day. The leading sources were sugar-sweetened drinks, desserts, and sweet snacks.
Now that you know the three guiding principles, here’s how to incorporate them into your diet.
How to Optimize a Vegan/Vegetarian Diet for Metabolic Health
Vegan diets (sometimes referred to as plant-based diets) contain no animal products or byproducts, including dairy, eggs, and in some cases, honey. Similarly, those on a vegetarian diet generally avoid meat, poultry, and seafood but often eat animal byproducts like cheese and eggs. That said, there are many variations of the vegetarian diet. For example, a semi-vegetarian might consume very little animal protein, an ovo-lacto vegetarian includes eggs and dairy, and a pescatarian may eat fish and avoid all animal protein. The foundation of both vegetarian and vegan diets is vegetables, fruits, whole grains, nuts, and seeds.
The metabolic benefits: The produce, nuts, legumes, and seeds that make up the foundation of vegan and vegetarian diets are high in dietary fiber and polyphenols, which are associated with a healthy microbiome and anti-inflammatory action. Several studies have shown the health perks of avoiding meat consumption. One recent review found that 17 out of 22 studies reported an association between a plant-based diet and weight loss or BMI improvements. The researchers concluded that there is sound evidence that a vegetarian diet is associated with healthier weight, body mass index, and fat mass distribution in the body. All of these things are linked to better metabolic health.
The potential metabolic pitfalls and what to do about them: Vegetarian and vegan diets can pose some potential risks to metabolic health. For instance, those following an unbalanced vegan diet may be deficient in essential nutrients, such as protein, omega-3 fatty acids, iron, vitamin D, calcium, zinc, iodine, and vitamin B12. Vegan and vegetarian eaters may assume that all vegetarian or vegan foods are metabolically healthy, but that is not the case. These diets often contain some plant foods, including potatoes, squash, and beans, that are high in starch and may cause blood sugar spikes in some people.
Vegetarians and vegans may also eat a lot of pasta, bread, and other foods made from highly processed wheat. Studies have shown that grain-rich diets can negatively impact blood sugar. But the type of grains you eat may make a difference. A meta-analysis of existing research showed that whole-grain intake is negatively associated with the risk of metabolic syndrome, while refined-grain intake is positively associated with the risk. (Some Levels advisors still suggest limiting whole grains, which can cause blood sugar spikes for some people.) If you eat grains, stick to nutrient-rich whole grains as much as possible.
If you’re on a vegan or vegetarian diet:
- Put whole fruits and vegetables on your plate first. Instead of thinking of this diet as devoid of meat or animal products, consider it a diet rich in a diverse range of nutritious, fresh, plant-based foods. This means avoiding processed and packaged foods, and emphasizing fresh, whole foods.
- Make sure you’re getting enough of the micronutrients that unbalanced plant-based diets can lack. According to Zoë Atlas, lead clinical dietitian at Laguna Honda Hospital and Rehabilitation Center and a Levels contributor, “Focus on nuts and seeds and legumes that have a high concentration of micronutrients that are important for vegans such as omega-3s and zinc.”
- Don’t be afraid of fortified foods. You don’t want to eat too much packaged food, but some fortified foods can help cover your nutritional bases if you’re on a vegan diet. “You can supplement your diet with certain fortified foods, including meat analogs, nutritional yeast, soy and unsweetened almond milk, and tempeh, which are often fortified with vitamin D and B vitamins,” Atlas explains.
- When you eat plant-based foods high in starch, like potatoes or beans, consume them with protein and healthy fats to prevent your blood sugar from spiking. Whenever possible, eat the protein and fat first, as this can slow gastric emptying and lead to a reduction in post-meal glucose levels. “For example, if you eat a sweet potato, pair it with avocado and tofu to slow the absorption of carbohydrates,” advises Atlas.
How to Optimize an Intermittent Fasting Diet for Metabolic Health
In recent years, intermittent fasting (IF) has become a popular way to lose weight and support metabolic health. IF commonly involves eating within a short window each day and going 12 or 16 hours between dinner one day and breakfast the next (also called time-restricted eating).
Other fasting methods include alternate-day fasting and the 5:2 method, in which you drastically reduce your calorie intake two days a week.
The metabolic benefits: According to research, IF may effectively reduce obesity, diabetes, and cardiovascular disease. The benefits are independent of weight loss, suggesting there’s more to IF’s positive effect on metabolic health than reducing weight. This has to do with IF’s ability to increase metabolic flexibility, which refers to your body’s ability to toggle between a fed and fasted state. When you’re more metabolically flexible, you can easily switch between burning sugar or fat for fuel, depending on what and when you eat. Metabolic flexibility is associated with stable blood sugar levels, while metabolic syndrome, Type 2 diabetes, and chronic inflammation are associated with metabolic inflexibility.
The potential metabolic pitfalls and what to do about them: There are some possible metabolic risks to keep in mind. A handful of studies have shown that IF is associated with an increased likelihood of engaging in binge eating behaviors. This can hurt your metabolism by affecting the production of leptin, a hormone that signals your brain to stop eating when you’re full. Binge eating also has adverse effects on blood sugar health, increasing fasting glucose levels and leading to dramatic insulin responses.
Some intermittent fasting plans claim you can eat whatever you want as long as it’s within the prescribed eating window. But following the same guidelines above, especially when you break your fast, is still vital for overall health. “If you’ve been fasting, your blood sugar will be low,” Atlas says. “If you eat something like a carb-rich bagel, you’ll give yourself a massive spike.” Instead, she recommends breaking your fast with some eggs with vegetables or a low-sugar green smoothie with chia seeds and almond butter.
If you practice intermittent fasting:
- Break your fast with a simple meal rich in fiber, protein, and healthy fats. Try one of these 10 breakfasts unlikely to spike blood sugar.
- Prioritize unprocessed, quality foods rich in nutrients. Cut down on the number of carbs you eat. Some helpful ideas: substitute zucchini noodles for pasta and use lettuce wraps or sliced vegetables for sandwiches instead of bread.
- Experiment with different types of fasting windows until you find one that feels ideal for your schedule and lifestyle.
How to Optimize a Keto Diet for Metabolic Health
The ketogenic diet is a low-carb, moderate-protein, high-fat eating plan. A keto diet is typically 70% fat, 20% protein, and only 10% carbs. Eating keto means consuming so few carbohydrates that your body needs to switch from burning glucose for fuel to burning fat for energy—a process known as ketosis. The keto diet eliminates most fruit as well as higher-carbohydrate vegetables like yams, beets, and parsnips.
The metabolic benefits: The ketogenic diet has been studied extensively and has shown many metabolic advantages. A few of the biggest: It releases ketones, which are associated with fat loss and an anti-inflammatory effect. They also indicate that your body is burning fat instead of glucose, which can help train your body to be more metabolically flexible. It also lowers the body’s concentration of hunger hormones. Other research shows that ketones have appetite suppression effects, and 20 days on a keto diet has been linked to a reduction in resting respiratory exchange ratio, a common way of measuring basal metabolic rate.
The potential metabolic pitfalls and what to do about them: The popularity of this diet has led to an abundance of packaged keto foods on grocery shelves. Beware foods labeled “keto-friendly” or “low in net carbs” that lack nutrient density and contain additives and preservatives. Some may also contain trans fats, which can trigger changes in your cells that lead to inflammation, while others rely on high amounts of sugar alcohols, which can cause GI problems, and artificial sweeteners, which can still impact insulin and glucose. Sticking with whole foods is still best. Also, some women experience inflammation or gain weight on keto, according to Sara Gottfried, MD, the author of Women, Food and Hormones. “What works for men doesn’t necessarily work for women [when it comes to nutritional ketosis],” she explained in an interview with Levels.
If you follow the keto diet:
- Eat plenty of leafy greens and cruciferous veggies. As Dr. Gottfried shared about her experience with keto, “…if I was getting the whole foods that I needed—especially the cruciferous vegetables rich in sulforaphane that help phase 2 of liver detox, as well as the allium vegetables that helped me produce glutathione—together these foods helped me detoxify and respond better to keto.”
- Focus on eating and cooking with high-quality fats and oils, like olive oil, avocado oil, butter and ghee, and coconut oil, to reduce inflammation and insulin sensitivity.
How to Optimize a Mediterranean Diet for Metabolic Health
The Mediterranean Diet is often hailed as the easiest and most satisfying way to eat to prevent disease, and research has confirmed its effectiveness. The principal components of the diet are a high consumption of vegetables, fruits, fish, olive oil, and unrefined grains, and a moderate consumption of dairy products and even wine. Those who follow this plan eat fewer meats and carbohydrates.
The metabolic benefits: The Mediterranean Diet can support metabolic health thanks to its high fiber content and healthy monounsaturated and polyunsaturated fats. One randomized controlled trial on almost 2000 people with metabolic syndrome showed that 28% of participants who started eating a Mediterranean diet no longer met the criteria for metabolic syndrome 4.8 years later. They also had less belly fat and better blood glucose than participants who followed a low-fat diet for the same study period. Research shows that a Mediterranean diet can prevent Type 2 diabetes and promote better cognitive health, which is thought to be directly related to metabolic health.
The potential metabolic pitfalls and what to do about them: The Mediterranean Diet includes grains—sometimes lots of them. Levels glucose data shows that even unrefined grains like rice and oats can cause blood sugar spikes when eaten alone or in large quantities. So while many physicians still recommend whole grains over refined grains, large amounts of unrefined whole grains can spike blood sugar.
If you follow the Mediterranean Diet:
- Be deliberate about when you eat grains and starches. According to Atlas, how your body responds to them can change depending on the time of day. “Insulin sensitivity tends to be higher in the morning, and everyone is different, so pay attention to how grains and starches affect you and optimize when you eat them,” she suggests.
- Keep alcohol intake to a minimum. The Mediterranean Diet includes moderate amounts of alcohol, but it’s unclear how alcohol may affect metabolic health. Some studies show a beneficial effect of light alcohol consumption on insulin sensitivity and cholesterol levels.
How to Optimize Paleo and Whole30 Diets for Metabolic Health
Following a Paleo diet means eating like people in the Paleolithic Age did. There are different categories of Paleo dieters, but most stick to foods in their most natural form—meat, fish, vegetables, nuts, and seeds. They avoid processed foods and refined sugars tied to the modern era, such as dairy, grains, and legumes. A Paleo diet tends to be high in protein. Whole30 prescribes a very similar eating style but differs in that it’s designed as a 30-day elimination diet, which includes the elimination of alcohol and all forms of sugar.
The metabolic benefits: Studies have found that eating Paleo can lead to weight loss, which can lead to better metabolic health. A Paleo eating plan may also improve the risk factors for cardiovascular disease and positively affect insulin sensitivity and glucose tolerance.
The potential metabolic pitfalls and what to do about them: Because those on the Paleo diet eat no whole grains and may avoid many legumes, they risk not getting enough fiber. Fiber is essential to metabolic health since it slows the absorption of food in the gut and promotes the production of short-chain fatty acids that are linked to improved insulin sensitivity and weight regulation. Fiber is also crucial to better gut health by keeping gut inflammation down and protecting the gut’s mucus membrane. Beyond fiber, avoiding whole grains and dairy may put Paleo dieters at risk for nutrient deficiencies like calcium, thiamin, and riboflavin.
There’s a chance the high amounts of fat and animal protein in a Paleo diet may also be problematic, although more research is needed. For example, a study published in 2019 that followed Paleo dieters for four weeks showed that they had increased levels of trimethylamine-N-oxide (TMAO) concentrations—a metabolite produced by gut bacteria that’s associated with cardiovascular disease and atherosclerotic plaque—although the changes were not statistically significant, so more evidence is needed to draw any conclusions.
If you follow the Paleo or Whole30 diet:
- Incorporate plenty of fiber-rich vegetables into your meals to ensure you meet the minimum recommendation of 22-34 grams of the nutrient per day (Levels advisor Dr. Mark Hyman recommends aiming for closer to 50 grams per day).
- “Make sure you’re consuming a variety of fruits and vegetables,” Atlas says. ”It’s easy to get stuck in a food rut where you eat the same thing every day.” Eat a diverse diet to help cover your micronutrient bases and ensure that you get enough nutrients like calcium, thiamin, and riboflavin.
- Consider a flexible approach that optimizes a Paleo diet for metabolic health by incorporating select farmed foods in controlled quantities and avoiding processed meats, which have been linked to increased cardiovascular risk and insulin resistance.
Low-Calorie Diets and Metabolic Health
A low-calorie diet has long been the go-to method for maintaining and losing weight. Many who follow this plan subscribe to the “calories in, calories out” equation and believe the key to maintaining a healthy weight is to burn more calories than they consume.
The metabolic benefits: Counting calories can be a valid way to lose weight. According to a meta-analysis of several diet programs and more than 50 published articles, calorie restriction was the factor most clearly associated with weight loss. In addition, a combination between the ketogenic diet and a very low calorie diet (a diet involving eating 800 calories a day or fewer under the supervision of a clinician) are recommended by physicians for cases of severe obesity and obesity associated with Type 2 diabetes, hypertension, and high triglyceride levels.
The possible metabolic pitfalls and what to do about them: One metabolic pitfall with a low-calorie diet is that it’s extremely difficult to sustain for more than a few weeks or months. In fact, research estimates that only about 20 percent of overweight Americans succeed at maintaining a 10% body weight loss for one year. In addition, very low calorie diets can lead to symptoms like dizziness, fatigue, and bloating.
And then there’s the food typically consumed on a low-calorie plan. When you count calories, it’s possible to focus more on food quantity than the composition of your meals and how those foods affect your metabolism. This can be problematic because how the body uses energy is an incredibly complex process influenced by several interdependent hormonal pathways. One of those pathways involves insulin, which is intricately involved in fat storage and weight gain. When insulin is high, it impairs the body’s ability to burn fat for energy. In other words, your calorie-counting efforts might be in vain if you’re not focusing on maintaining healthy blood sugar and insulin levels and eating foods that help you achieve that.
If you follow a low-calorie diet:
- Prioritize quality. If you’re limiting calories, food quality is paramount. Grass-fed beef has higher levels of omega-3 fatty acids than grain-fed beef, for instance. Organic fruits and vegetables have between 20 and 40 percent higher antioxidant levels than conventional ones. That’s the equivalent of eating two extra portions of fruit and vegetables daily, the authors of one study said.
- Be sure to eat enough calories. “If you’re going to restrict calorie intake, you need to make sure you’re getting a variety of foods and enough food to keep your energy levels where they need to be,” Atlas explains.
- Be mindful of carb intake to manage glucose and insulin. Consider proven strategies like eating carbs earlier in the day; pairing them with fiber, fat, or protein; consuming vinegar beforehand, or taking a walk afterward.
