How Much Exercise Is Enough?

I wanted to make a quick post about the new Current Biology study that’s making the rounds: Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans. This paper demonstrates that there is a threshold for how much exercise will lead to weight loss. Ultimately they found that exercise for burning calories isn’t linearly additive, so more isn’t always better. This explains why it’s impossible to simply exercise your way to weight loss (without considering nutrition) but also why endurance athletes don’t see significant weight loss when they increase their mileage from already high to super high.

The underlying mechanism for this phenomenon isn’t certain, but the authors hypothesize that it is partly because increased exercise leads to an increased exercise efficiency (and corresponding downshift in metabolism), but also that we as a species have a set range for daily energy expenditure regardless of who we are, where we live or what we do. The “what we do” portion (physical activity) contributes to under 10% of our daily energy expenditure- the other 90% is shared among all of us, and is essentially the energy it takes to be alive.

In practical terms, what does this mean for people who care about their health, fitness and appearance?

1. If you want to lose weight, you need to eat better.
2. Exercise is still very important and will increase your fitness and health, but not necessarily your body composition.
3. Lifting weights trumps cardio for long-term body recomposition. Why? Because although this study demonstrates that exercise itself has a daily threshold, it doesn’t mention that you can indeed increase your baseline metabolic rate by increasing muscle mass. Resistance training builds muscle and muscle increases metabolic demand.
4. Prioritizing daily activity will be more productive for weight loss than one or two long bouts of exercise each week.
5. Running long distances is beneficial for competitive runners who want to improve their ability to run long distances. Running long distances is an inefficient strategy for fat loss.

So how much exercise is enough? As with most answers, it depends. The type of exercise is a major factor as well. Here are some good guidelines:

• Be active every day: Walk when you can, take the stairs and generally make more time to move and less time to sit. Remember that each day you will burn a certain number of calories simply by being alive and you have the ability to burn more through additional exercise. This daily added amount has a threshold, but by doing nothing extra you’ve wasted an opportunity to optimize energy expenditure.
• Add 1 hour of resistance training 3-5 times per week. Not only will this put you near your optimal energy expenditure most days but you’ll be building muscle and raising your baseline metabolic demand.
• Don’t waste your time doing the same exercise at the same pace every day. Your body adapts quickly and will become efficient at preserving energy if all you do is jog sluggishly each day. As a general rule of thumb you’ll get more value from short, intense interval sessions than you will jogging at a steady pace.
• Prioritize nutritious foods like fresh cuts of meat and produce as the foundation of your diet. Being consistent over time with a nutrient-dense diet is the key to health and body composition.

The moral of the story is that although exercise is an important part of a healthy lifestyle, excessive exercise won’t lead to excessive fat loss. If you’re consistent with a healthy diet and active lifestyle, overall health and a lean body composition will eventually follow suit.

If you have any questions, don’t hesitate to drop me a line!

– DW