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About a year ago, Dr Peter Attia interviewed bodybuilder, powerlifter, and nutritional scientist Layne Norton in his The Drive podcast. They discussed the subject of weight loss without muscle loss, and we wrote an article about it summarising the key points. Recently, Layne Norton returned to the podcast for a part 2, which can be found here. If you’re trying to lose weight, gain muscle, or are simply interested in how the body handles its energy, we recommend you give it a listen, as it contains plenty of valuable information. Here are some of the key takeaways:

The Challenges of Weight Loss

Many people attempt to lose weight by counting calorie intake and calorie expenditure. They assume that if they expend more calories than they take in each week, they will lose weight consistently. There are multiple reasons why this strategy often fails:

Between 50% and 70% of the calories the average person expends each day is not used for exercise, but rather in fundamental metabolic processes (this is called the basal metabolic rate or BMR). Not every person has the same BMR, and it is not easily measurable by the average person.
When calorie intake is reduced, metabolic adaptations occurs. BMR slows, physical activity is subconsciously reduced, and so weight loss plateaus.
Wearable devices tend to overestimate the calories consumed during exercise.
People are typically very bad at estimating how many calories they consume. Studies have found that obese people tend to underestimate calorie consumption by 30 to 70%, while lean people underestimate by 10 to 18%.
Food labels are not perfectly accurate when it comes to calorie content.
Weight has some natural, random fluctuation. It is important to weigh yourself multiple times throughout the week, preferably at the same time of day, and take the average of those measurements.

What Strategies Define Effective Weight Loss?

There are many approaches to losing weight, but what are the key differences between those who succeed and those who don’t?

Tracking calories aids weight loss. Tracking one’s calories is like keeping a budget: it may not be 100% accurate, but it’s much more accurate than guessing. Calorie counting also has a behavioural effect: people who are tracking their calorie intake are more mindful of what they eat and are less likely to snack because they know they need to track it.
Successful dieters use some form of restriction in their diet, such as calorie counting, time-restricted eating, fasting, or restricting one or more types of nutrient.
It is important to choose the form of diet that feels the least restrictive, and this is different for everyone. No one diet is superior.
Successful dieters don’t binge eat and rarely snack – they eat defined meals. When they stop snacking, many people find they aren’t actually any hungrier.
Avoiding alcohol can help – alcohol is calorie dense and encourages poor food choices.
Successful dieters have supportive friends/family. Encouragement and offers of help are better forms of support than criticism/micromanagement.
Undergoing a prolonged fast (3-5 days) can be valuable even if you only do it once, because it teaches you that hunger comes in waves and can be endured. The vast majority of people are capable of such a fast without incurring health risks. After fasting for 5 days, most other diets become comparatively easy!
Exercising is important not only as a means of increasing calorie expenditure, but because it increases the responsiveness to satiety hormones (it can actually make you less hungry).

Losing Fat Without Losing Muscle

Becoming very lean while maintaining a high muscle mass is very difficult to do without drugs, though it is possible. This is because the amount of fat mass vs muscle mass lost when dieting depends on how much fat or muscle already exists.

When someone who is overweight or obese loses weight, this is almost 100% fat tissue.
As you become leaner, the metabolism begins to conserve fat tissue and break down some muscle instead. This is because from a survival perspective, the fat tissue is more valuable than muscle during starvation. Muscle has a high maintenance cost, while fat does not.
From a bodybuilding perspective, the best way to look as muscular as possible is to be as lean as possible. This is why drug-free bodybuilding is very hard.

Effects Of Different Types Of Nutrient On Energy Expenditure

Can consuming a high proportion of a certain macronutrient (carbohydrates, proteins or lipids) affect the metabolism in such a way as to increase calorie expenditure? Until relatively recently, this was an open question.

A study in 2019 suggests that people on a ketogenic diet (low carb, high fat) expend 50 to 150 more calories each day than people eating a normal diet containing the same number of calories.
This study wasn’t perfect, and some argue that the method used to measure energy expenditure (doubly labelled water) doesn’t work well in ketogenic diets.
Either way, the evidence so far suggests that weight loss from ketogenic diets is mainly due to reduced calorie intake.

The Importance Of Protein, Exercise, and Muscle Strength For Health And Lifespan

Exercise, and specifically strength training, is possibly the most important thing anyone can do to improve their health and lifespan.

Exercise, even in moderate amounts, improves metabolic health substantially compared to being sedentary. Weight loss is not required for this.
High muscle mass is very beneficial, more so than good food choices, and protects against poor food choices.
The idea that heavy lifting will lead to pain in old age is erroneous because, according to Layne Norton, ”You’re going to be in pain when you’re older regardless. Do you want to be in pain and strong or in pain and weak?”
It is still possible to build muscle in old age. A 16 week study in 80 year-olds squatting with increasing depth found that participants were able to increase their lean mass by amounts similar to that which a 20 year-old can achieve as a proportion of their starting lean mass. 20 year-olds obviously have much higher starting lean mass, but this shows that it’s never too late to build muscle.
It’s interesting to note that the frequency of deaths due to accidents is similar across age groups, but the causes are different. Young people die in car accidents while the oldest people from accidental falls.
There are even analyses suggesting that the majority of deaths in the over-65s are linked to low muscle strength in some way. The hazard ratio for not being strong compared to being strong is estimated at 3.2 – you are 3.2 times more likely to die from any cause if you have low muscle strength compared to high strength. This is a larger effect than smoking.
The health and longevity benefits from just three 30-40 minute sessions of resistance training a week are enormous.

The above is just a summary of some topics discussed, but there’s plenty more valuable information to be learnt from the discussion, including what a 50 year-old should eat, what supplements they should take, and what training program they should follow to ease themselves into resistance training.