When you’re in a caloric deficit, your body is eating you alive.
Your goal as a dieter is to make sure your body “eats” as much fat and as little muscle as possible.
One of the best ways to keep your body from devouring your muscle tissue is to give it another source of protein — dietary protein.1,2
Think of your caloric deficit as a lion that’s about to eat you. If you give the lion another source of meat, you might be able to get away without getting bitten.
Likewise, if you don’t eat enough protein while dieting, you’ll lose more muscle and less fat.
The problem is that your protein needs can change over time based on several factors, which can make it hard to pinpoint exactly how much you need to avoid muscle loss. Another problem is that most of the recommendations for protein are not designed for dieting athletes, like you.3-5
However, we do have enough research at this point to make some educated guesses as to how much protein you need to keep the lion happy.
3 Reasons You Probably Need More Protein than the Average Person
Researchers have used nitrogen balance studies to estimate the minimum amount of protein you need to stay reasonably healthy. These studies aren’t perfect, but they’re still a useful tool for determining your protein needs.3,4,6-8
They’ve used this data to develop what’s known as the “Recommended Daily Intake,” or “RDI, for protein.
The current RDI for protein is 0.8 grams per kilogram of body weight per day (g/kg/day). This is the minimum amount needed to keep 97.5% of people over the age of 19 healthy.3,4,9 It’s the standard protein intake for most diet recommendations.
If you’re sedentary or lightly active and not in a caloric deficit, you probably don’t need to eat much more protein than the RDI.
However, if you’re trying to lose fat while maintaining your muscle mass and athletic performance, there are three main reasons why the RDI is probably too low for you.
1. Your protein needs increase when you cut calories.
Your body is always breaking down and rebuilding tissues. When you’re in a caloric deficit, your rate of tissue breakdown rises above your rate of tissue growth, and you lose weight.10 You’ve let the lion out of the cage.
When this happens, your body loses more protein than it retains, and you need to eat more protein to maintain your lean body mass.11-14
When people restrict their calorie intake, those who eat more protein generally lose less muscle and more fat.2,15-23
In general, the larger your caloric deficit, the more your body tries to cannibalize your muscle tissue.24,25
Eating more protein can help prevent this to a degree, but after a point you’re probably going to lose some muscle mass if you cut calories low enough.
In most cases, overweight dieters need to eat at least 1.4-1.6 grams of protein per kilogram of body mass to avoid losing muscle.9,17,19,21 That’s about twice the RDI. If these people lift weights, they can usually eat slightly less because strength training also helps preserve muscle mass.26
2. Your protein needs increase as you get leaner.
The less body fat you have, the more protein you usually need to prevent muscle loss while dieting.3,6
When your body has thousands of extra calories stored as fat tissue, it’s generally less likely to break down your muscles. The reverse is also true, however.
Obese people can maintain their muscle mass while eating 800 calories per day, if they eat about 1.2 g/kg of protein and lift weights.26
Most studies indicate that leaner athletes may need more protein to prevent muscle loss when dieting to lower body fat levels.27,28 The most recent and comprehensive review, authored by Eric Helms, indicates that lean athletes need around 2.3-3.1 grams per kilogram of lean body mass to avoid losing muscle while dieting.6
That might seem like a lot, but it’s actually not that much more than obese people when you adjust for their body composition. For example, in one study obese women ate 1.6 grams of protein per kilogram of total body weight. When you apply this same amount to their lean body mass, however, it’s actually 3.2 grams per kilogram.19
Lean people probably need more protein than overweight people to avoid losing muscle while dieting. When you adjust for your lean body mass, however, the differences aren’t huge.
3. Your protein needs increase during intensive and/or high-volume progressive training.
If you’re challenging yourself with more volume, intensity, or variety in your training, you might need to eat more protein while dieting.
Even if you’re not in a caloric deficit, there’s good data that both strength and endurance athletes need more protein than the RDI to perform at their best.3-5,8,29
Dieting is another kind of stress, which probably increases your protein needs even more.3-5,8,30
If you want to maintain your muscle mass and performance while dieting, you also need to maintain the intensity of your training. Eating more protein probably makes that easier.
How to Set Your Protein Intake While Dieting
Here’s what we know so far.
- When you’re in a caloric deficit, you need to eat more protein than normal to avoid losing muscle mass. The larger your deficit, the more protein you generally need, to a point.
- If you’re leaner, you need more protein than overweight or obese people to avoid losing muscle.
- If you’re training hard while you’re in a caloric deficit, you probably need even more protein than normal to avoid losing muscle.
All of the above factors are also additive. If you’re in a large calorie deficit, you’re at a low body fat percentage, and you’re training hard, you’ll probably need a lot more protein than the standard RDI.
This doesn’t mean more is better for everyone, but lean, dieting athletes almost certainly need more protein than most other people.
Use this chart to estimate your protein needs:
|No calorie deficit, minimal training, or less focused on maintaining muscle mass.||1.2-2.0 g/kg|
|Small to moderate calorie deficit, with progressive training.||1.8-2.4 g/kg|
|Medium to large calorie deficit, with progressive training.||2.3-3.1 g/kg|
These values are for your lean body mass, not your total body mass.
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