Looking to start an exercise program to lose weight? ...Read this first.

Contents
1. Overview
2. Can you lose weight with just exercise?
3. Does anything work?
4. Learnings
5. References
The gist
Research shows little to no relationship between energy expenditure and body fat levels. (A gigantic study on 34 079 women concluded that, to prevent fat gain with exercise alone, women must exercise for approximately 60 minutes every day. The amount needed to lose fat was undetermined.)
The #1 reason for this is a subconscious increase in food intake. However, a conscious increase in food intake is also a contributor as people who are told they are "exercising" consume 41% more calories than those who are told they are being active for "fun".
A second contributor for some individuals is a reduction in subconscious activity levels away from the gym (termed: NEAT).
Nutrition, and in particular taking control over energy "in", is the missing key to allowing fat loss to occur with exercise.
Nutrition + exercise interventions result in a rate of fat loss that is 3-10x faster than exercise alone. Nutrition accounts for at least 70% of this fat loss.
You should still exercise as it is likely the single most important modifiable determinant of your health and longevity.
If your goal is to lose fat, create a calorie deficit, either through consuming fewer calories than you are now, increasing your activity, or both. Just make sure that you are not re-consuming these calories by not paying attention to your nutrition.
A calorie deficit is required to lose weight [1]. According to the laws of thermodynamics, there are no ifs, ands, or buts about this.
However, many factors affect this energy balance equation that sometimes makes it seem like expectations and reality don’t quite line up. This is because it is more complicated than it seems on the surface. Today we’re going to be discussing how focusing on only one piece of the equation may influence other pieces without you even noticing.
Can you lose weight with just exercise?
Let’s look at some of the largest studies to date on this question:
