Exercise is hard. If you live in a developed country in 2025 (especially a car-centric one), it’s incredibly easy to avoid exercise and overeat. In order to self-motivate myself to exercise, I wrote this piece to summarize some quantitative benefits of exercise.
The Expectations
Many developed countries publish standards for how often, and how hard, you should be exercising. I’ll be mostly referring to the CDC’s recommendations in this post, because many scientific studies also use this standard, and the CDC’s recommendations basically mirror other organizations (like the WHO).
The CDC pulls its recommendations from a DHHS (another U.S. agency) 2018 publication, titled Physical Activity Guidelines for Americans, 2nd edition. It contains these specific recommendations for adults:
- Aerobics: 150-300 minutes per week of moderate-intensity aerobic exercise, or 75-150 minutes per week of vigorous-intensity aerobic exercise, or an equivalent mixture of both
- Muscle/strength: 2 days per week of “muscle-strengthening activities” (of moderate or greater intensity) that involve all major muscle groups (legs, hips, back, abdomen, chest, shoulders, and arms)
Unfortunately, only 47% of American adults meet the aerobics guideline, and only 24% meet both. If you’re an American reading this, you’re probably not doing enough exercise. This is obviously a negative effect on the country— due to multiple factors (beyond just exercise), ~74% of American adults are either overweight or obese.
What Counts as “Moderate” or “Vigorous”?
Rather than using these subjective terms, let’s make things concrete. Every activity you can do can be measured into a Metabolic Equivalent of Task (MET) value. For example:
- Sitting and watching TV, sleeping, or listening to music are all 1.0 MET.
- Descending stairs, or carrying groceries, are 3.5 MET.
- Running at 10 minute per mile pace is 9.3 MET.
- You can find several other examples at pacompendium.com.
When you perform a task’s MET for an hour, you get MET-hours. For example, carrying groceries for 2 hours would be 7 MET-hours (3.5 * 2 = 7).
The CDC does not publish weekly MET-hour recommendations, but a rough approximation is that you should aim for at least 9 MET-hours, or ~500 MET-minutes, of exercise per week. Understanding MET-hours is critical if you want to dive into the scientific literature surrounding exercise.
What Benefits?
The CDC publishes qualitative benefits for exercise like “improved sleep and quality of life”, and that’s great, but I want data. When I’m trying to convince myself to exercise, it’s a lot harder to shrug off specific datapoints like “people who meet these guidelines sleep 10% longer” (I just made that up— we’ll soon get to the stats).
Unfortunately, due to the inherent nature of science, it’s really hard to quantitatively say anything about anything. Every study is conducted differently; some studies account for confounding factors like age and wealth, and some don’t; some studies are likely biased; etc. I did what I could to collate some “good” studies to represent the best science has to offer, but I’m not a scientist :)
Let’s get on to the statistics.
The Statistics
Aerobics
If you meet the CDC’s aerobics guidelines:
- You will have a 25% lower risk of depression1.
- “Happiness” is notoriously difficult to accurately measure, so there are a lot more studies that measure the effect of exercise on depression or depressive symptoms.
- Exercise may be one of the best treatments for depression, potentially outperforming SSRIs2.
- You will sleep better3. More specifically, you will:
- Fall asleep a few minutes faster
- Spend a greater proportion of your time in bed actually sleeping
- Increase overall sleep time
- Self-report a large improvement in your overall sleep quality
- You will have a 29% reduced risk of all-cause mortality4.
- This 29% is relative risk. In other words, if you meet the CDC’s aerobics guidelines, your risk of death (of any cause) is 29% lower than your peers’ risk.
- For example, if your equivalent (but non-exercising) peer has a 20% mortality rate (meaning there is a 20% chance they will die in a year), you would have a 14.2% mortality rate (a relative reduction of 29%).
- For reference, a 30-year-old male in the USA has a 0.2332% chance of death each year.
- Exercising reduces the rate of certain cancers, heart disease, etc., but I decided not to list these separately— “all-cause mortality” is a catch-all.
- This 29% is relative risk. In other words, if you meet the CDC’s aerobics guidelines, your risk of death (of any cause) is 29% lower than your peers’ risk.
- You will live ~2.7 years longer5.
NOTE: were you expecting “weight loss” in this list? Shockingly, the evidence for weight loss from aerobics alone is not great. This study puts it well: “The evidence that exercise contributes significantly to weight loss and weight maintenance is not firmly established.” See further discussion.
Muscle-Strengthening
If you meet the CDC’s muscle-strengthening guidelines, you will receive these benefits in addition to any benefits from aerobics:
- You will have an 11% reduced risk of all-cause mortality4.
- Muscle-strengthening exercise appears to benefit bone health and reduce fall risk in older adults, but these types of dangers are captured in the reduction to all-cause mortality.
NOTE: I struggled to find specific scientific outcomes from muscle-strengthening exercises, beyond preventing certain types of injuries. There may be cognitive improvements in older adults, and insulin sensitivity improvements.
Conclusion
If you perform at least 150 minutes of moderate aerobic exercise each week, you will live a longer, happier life. There are specific, measurable improvements you will realize immediately after beginning this routine.
There’s nothing special about the number “150 minutes” of aerobic exercise per week. Even if you don’t hit 150, you should still try. There are partial benefits for partial completion (e.g., 18% lower risk of depression for only 75 minutes of moderate-intensity aerobics1).