With an estimated 39 percent of the global adult population being overweight or obese, weight loss has become one of the most desirable fitness goals today (1).

In this guide, we’ll break down the science behind losing weight, how you can lose a lot of fat rapidly, and what might be the best approach for long-term health.

Let’s dive in.

How to Lose Weight: 4 Crucial Factors

Despite the complexity surrounding the topic, weight loss, be it slow, moderate, or fast, comes down to creating and sustaining a calorie deficit (2). Consuming fewer calories than you burn is necessary for forcing your body to break down fat and lean tissue for the remaining energy it needs. Maintain a deficit long enough, and you will see yourself lose mass and weigh less.

Your rate of weight loss mainly depends on your calorie intake and activity level, which regulate how big the energy deficit is. Eating less food and moving a lot throughout the day will result in a considerable deficit and rapid weight loss. Conversely, enjoy more food, move less, and your deficit will be smaller, resulting in slower weight loss.

Additionally, you should ensure an adequate protein intake of at least 0.8 grams of protein per pound of body weight (3). For instance, if you weigh 190 lbs, that would mean eating at least 150 grams of protein daily. Doing so is necessary to supply your body with the building blocks needed to maintain muscle tissue (4). 

The third factor related to weight loss is physical activity. More specifically, doing some form of resistance training. Lifting weights or using your body as the resistance is necessary for stimulating your muscles and preserving lean mass (5). Doing so tells your body, “Hey, muscle is important, so don’t break it down for energy.” The great news is that just three sessions of 40 to 60 minutes are enough to cause that effect. Do various movements for all the major muscle groups, train with good form, and focus on progressive overload to reap the full benefits.

The fourth and final factor that goes into good weight loss is sleep. In one study from 2010, researchers found something interesting (6). Ten overweight but otherwise healthy individuals had to complete the same two-week diet protocol with at least three months of recovery. 

In one of the trials, subjects did a calorie-restricted diet and were allowed to sleep for up to 8.5 hours per night. In the second trial, subjects did the same diet but could only sleep for up to 5.5 hours. The participants lost an average of 6.6 pounds in both conditions, but here is the interesting bit:

When subjects could sleep more, they lost fat and muscle at a 50:50 ratio, which isn’t great or terrible. In contrast, when they could only sleep for up to 5.5 hours, they lost fat and muscle at a 20:80 ratio. With all else being equal, sleeping less resulted in significantly more muscle loss––only a fifth of the total weight loss came from actual fat.

Is Rapid Weight Loss The Way to Go?

While rapid weight loss is a desirable goal for many people, rushing the process could do more harm than good. The problem is that your body can only break down so much fat (adipose tissue) in a given period. So, by maintaining a considerable deficit, you’re more likely to lose muscle alongside the fat (7). As a result, you could end up skinny fat––being thin but having a layer of fat covering your body.

Rapid weight loss is also problematic because you’re more likely to feel incredibly deprived, increasing the risk of slipping up and binge eating. Plus, overly-restrictive diets are not sustainable and rarely work in the long run. You can follow such a diet for a few weeks, but what if you need months of being in a deficit to reach a healthy weight?
According to data, the optimal rate of weight loss is 0.5 to 1 percent of your body weight per week (8). That rate is quick enough to see steady progress but not too fast that you risk muscle loss or extreme hunger. People with a higher body fat percentage can lose up to one percent of their body weight, whereas leaner individuals should be more moderate and aim for no more than 0.5 to 0.6 percent weekly.

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