Intermittent fasting, balanced or keto diet? Food for thought

We all know that exercise and proper nutrition are important for a healthy body. But how much exercise and what is a good diet?

In a two-part series, we learn from UC Davis molecular exercise physiologist Keith Baar how our bodies respond to physical activity and how different diets affect our metabolism. Baar is Professor of Neuroscience, Physiology and Behavior, and Physiology and Biology of Membrane.

In celebration of National Nutrition Month (March), we’ll start with how balanced intermittent fasting and the keto diet affect our bodies.

Which is more important for weight loss and wellness: diet or exercise?

Our body will behave differently depending on the combination of physical activity and nutrition. It’s no secret that it takes a lot of exercise to change body weight. But nutrition allows us to regulate body weight better than exercise.

I always tell people that if you run a mile it’s 100 calories. If you then eat a piece of white bread or about 10 tortilla chips, that’s 100 calories. Thus, it is easier to manage your weight through nutrition, but increasing physical activity will help you better manage your health.

How do our current lifestyle and food choices affect our bodies?

Your body is designed to survive periods of feasting and famine. It has been programmed by evolution for ups and downs in eating and other stresses such as illness or the need to run.

What has happened in the last 20,000 years is that we have become more efficient – we are producing more food with less labor. This has led to what we call hypokinetic diseases, which are health problems that result from a person moving too little. We have also changed our diet to more frequent meals and more carbohydrate-rich processed foods. The result is more stimuli that are not ideal for maintaining healthy muscles and the rest of the body.

Why is it said that good food is good medicine?

Our muscles and immune system use very similar signals. They both want to turn on a protein known as the rapamycin mechanistic target (mTOR) when they need to respond to a stimulus, save calories, grow or fight an antigen. With our classic overconsumption of processed foods, we reach chronic levels of high mTOR protein activation and this leads to things like insulin resistance and chronic inflammation.

Then, when your body needs to react quickly—for example, when exposed to a high-carb food or a virus—it reacts slowly because the signal is drowned out by noise.

This is why many diets that improve longevity or health, such as low-protein and low-carbohydrate diets or time-restricted meals, target mTOR activity. On these diets, mTOR activity is significantly lower at rest. This is important, for example, if our body needs to respond to a virus. It has a much greater dynamic range and can quickly turn on the processes needed to respond to a threat. When we decrease mTOR baseline activity, we can also improve how the body generates energy by removing faulty mitochondria (powerful engines in cells), allowing our muscles and brain to perform better.

Is a balanced diet ideal for the body?

A balanced diet, including a variety of carbohydrates, proteins and fats, can be beneficial to the body if we allow periods when calories are low. One option is to consume about 10% fewer calories than you need. Another option is to limit your meal times by having periods around 5 pm a day when you don’t eat. Both of these strategies lower this baseline, but they can be very difficult for many people.

What about the benefits of a ketone (keto) diet?

The keto diet involves eating more fatty and protein-rich foods and fewer carbohydrates. The goal is to reach a state of ketosis as your body burns fat for fuel instead of sugar. This process results in the formation of acids known as ketones.

In our studies of keto diets in mice, we compared a low-carb group with a ketogenic diet group. The benefits we’ve seen in muscle for mitochondria, strength and endurance; in the brain prior to learning in memory; and in terms of life expectancy, all were better off on a ketogenic diet than on a low-carb diet. There is something about these ketones (beta-hydroxybutyrate) that is really good for our longevity, muscles and brain. But the keto diet has its risks, including weaker bones and the possibility of high cholesterol levels in some people.

Nutrition makes it easier to manage your weight, but increasing physical activity will help you manage your health better.” —Keith Baar, molecular exercise physiologist at UC Davis

Is intermittent fasting good for your health?

We would rather think of intermittent fasting as a time-limited diet. You have periods of fasting, then periods of eating.

The work of UCSD Professor Satchin Panda with different individuals and groups clearly shows that time-limited feeding can indeed have a positive effect. During fasting, your body resets the baseline of many things, including mTOR activity.

One of the things that also happens towards the end of a fast is that the body produces ketones, just like on a keto diet. However, if you’re on a regular diet but limit your meal times, you won’t get the full benefits of the keto diet. When the body undergoes prolonged fasting, it begins to produce ketones, but may not reach the levels required for therapeutic ketosis.

How do you see the future of dieting?

For our health and longevity, it would be great if we could eat a mixed diet, eat whatever we want, and still get the cognitive and muscle benefits of a keto diet. One important question: Is it possible to follow a regular diet and get ketones from supplements like keto esters or ketosalt drinks? In other words, can we get the benefits of the keto diet without its problems, like weaker bones and potentially higher cholesterol levels? Unfortunately, such a diet will not lead to weight loss, and whether it will improve muscle and brain function, we do not yet know.

Note: People with special dietary needs or medical conditions should seek advice from their doctor or registered dietitian.