Fat loss is about calories in versus calories out, but how much less should you eat to lose fat?
This is one of the hardest and most important parts of dieting. There are pros and cons to large and small deficits, and you may want to use both depending on your goals.
In this article, you’ll learn how different size deficits affect your body, and how to decide which is best for you.
The Top 4 Ways You Can Set a Caloric Deficit
1. Pick a specific number to achieve a certain rate of fat loss.
This is how most people set a deficit.
They decide they want to lose a certain amount of fat per week, usually about one pound. They know that one pound of fat has about 3,500 calories, so they figure out how many fewer calories they’ll need to eat per day to lose one pound of fat — 500.(1)
For most people this works well. It’s simple and achievable.
The problem, however, is that this size deficit might be too aggressive for some and too slow for others. If you’re already maintaining your weight at 2,000 calories per day, cutting your food intake by 25% might be too drastic.
In contrast, if you maintain your weight at 4,000 calories per day, you might be able to achieve a faster rate of fat loss with a larger deficit.
2. Set your calorie intake according to your body weight.
Instead of estimating your maintenance intake and then subtracting an arbitrary number, you set your calorie intake with fat loss in mind from the beginning.
For example, bodybuilders often use 10-12 calories per pound (22-26.4 kcal/kg) as a starting place for fat loss.
This approach is a little more customized to your individual needs because it accounts for differences in body size. However, this only takes into account your bodyweight, which is not always an accurate predictor of your total energy needs.
People who exercise more are going to have higher energy needs, and setting your total calorie intake according to your body weight could create an excessive deficit. For instance, if you have a 150 pound endurance athlete who burns 4,000 calories per day, they’d only be eating 1,500 to 1,800 calories per day if they followed the same guidelines as many bodybuilders.
For sedentary people with lower than average calorie needs, this deficit might be too small relative to their goals.
3. Cut calories as much as you can.
Instead of worrying about your maintenance needs, achieving a certain rate of fat loss, or setting calories according to your bodyweight, you simply eat as little as possible. You might find that you can eat 800 calories per day without chewing off your hand, so you set that as your daily calorie intake.
This option is generally not a great plan. As you’ll learn in a moment, large deficits are not appropriate in all situations.
Most of the people who use this method aren’t great at estimating their calorie intake, which is why they avoid figuring out their calorie needs in the first place.
This approach also makes it hard to adjust your calorie intake as you diet. This isn’t to say that large deficits are always bad, but using “as little as possible” as a guide is not an optimal way to set your calorie intake.
4. Set calories as a percentage of your maintenance intake.
You estimate your maintenance calorie intake, and then subtract a percentage from your maintenance. If you need 2,000 calories per day to maintain your body weight, and you slash your calorie intake by 20%, then you’d eat 400 calories less per day, or 1600 calories.
This is generally the best way to set your calorie deficit.
This method scales your calorie intake to your energy needs instead of assigning an arbitrary number to achieve a certain rate of fat loss.
People with higher energy needs will be able to eat proportionally more and lose fat. People with lower energy needs will have a deficit that’s more appropriate for their calorie intake.
With that in mind, let’s learn which size deficits are most appropriate for your goals.
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How Different Size Deficits Affect Your Body
Big and small deficits can be perfect or completely inappropriate, depending on the context. To decide which is right for you, you need to learn the pros and cons of both approaches.
Here’s how we’re going to define the size of caloric deficits:
Small: 15% below maintenance calories.
Medium: 15-25% below maintenance calories.
Large: 25% below maintenance calories.
Think of your caloric deficit as a spectrum from small to large. Smaller deficits tend to cause fewer changes, both positive and negative, and larger deficits tend to do the opposite. Here are the different variables that change based on the size of your caloric deficit.
1. Your rate of fat loss.
Larger deficits produce the highest rates of fat loss and vice versa. (2-4)
If you severely cut calories, then you don’t have to diet for as long and you’ll reach your goal weight sooner.
Assuming you need a more typical 2,500 calories per day to maintain your weight, here’s what your rate of fat loss would look like using these three deficits:
If you have higher than average energy needs, a small deficit can still help you lose fat at a decent rate. If you need 4,000 calories per day to maintain your weight, a 10% deficit will give you about 0.8 pounds of fat loss per week. This is one of the reasons bodybuilders often do lots of cardio (5) — having higher total energy needs means you can lose more fat at a proportionally smaller deficit.
2. Your adherence.
Some people are better at sticking to small deficits, and some people prefer large ones.
Larger deficits tend to be harder to stick to as they require more exercise and/or food restriction and are generally harder to achieve. Smaller deficits are usually easier to maintain. That’s not always true, however, because larger deficits also help you lose weight faster. For some people, losing a lot of weight quickly makes it much easier to stick to the diet over the long-term.(2,6)
Larger deficits can also make some people unbearably hungry. This isn’t true for everyone, however. Some data has shown that hunger tends to drop at about 800-1200 calories per day.(7-10<) Other people don’t mind the hunger and are willing to put up with it if it means they get lean faster.
3. Impact on your training.
Large deficits make it harder to train, recover from workouts, and improve your performance.(11-14) In some cases, the negative effects of dieting don’t outweigh the performance benefits of getting leaner.
Even if you’re not a performance athlete, maintaining the intensity of your strength workouts is essential for [preserving your lean body mass while dieting](https://evidencemag.com/fat-loss-podcast/). If you massively slash calories and your strength drops, it’s more likely you’ll lose muscle.
4. Muscle loss.
Most studies have found that the larger your caloric deficit, the more muscle you’ll lose.(15-21) However, most of the people in these studies were not strength training or eating enough protein to prevent muscle loss.
If you set up your diet correctly with adequate protein and strength training, then you can usually limit muscle loss to a very small amount, if any.
If you’re already fairly lean, larger deficits will generally make you lose some muscle even with strength training and adequate protein.(22,23)
If you’re overweight, however, then you can usually restrict your calorie intake more without losing as much, if any, muscle. Your body has thousands of extra calories to burn from fat, so it’s less likely to break down your muscle for energy.
5. Metabolic adaptation.
When you cut calories you burn fewer calories for a variety of reasons, mostly because you move less.(24-27) This is generally more of a problem with larger caloric deficits.
Larger deficits also tend to cause a greater drop in leptin, thyroid, and other hormones while smaller deficits have a smaller impact. Any time you cut calories, you’re going to experience some of these effects, but they tend to be less severe with smaller deficits.
Here is a summary of the pros and cons of large, medium, and small deficits.
Large Calorie Deficit = >25% Below Maintenance
- Fastest rate of fat loss — you can get lean in weeks rather than months.
- Provides huge immediate gratification, which can encourage long-term adherence to weight loss. Kickstarts your motivation to diet.
- Reduces the chance you’ll eat too much. The size of the deficit gives you a larger margin of error when monitoring your calorie intake.
- Destroys high volume and/or intensity exercise performance. Increases the risk of illness or injury and makes training miserable.
- Requires you to eat much less food. Most of the people who need to lose massive amounts of fat can’t or won’t exercise much, so the deficit is going to have to come from their diet.
- Intimidates some people, which could compromise their adherence.
- Requires extreme self-deprivation and food restriction which can encourage eating disorder symptoms like binge eating and yo-yo dieting. After setting your protein intake, there isn’t much room for anything else.
- Increases risk of nutrient deficiencies if sustained for too long.
- Causes more muscle loss than less severe deficits, especially in lean people. Very overweight people can sometimes use large deficits without losing muscle, however, if they strength train and eat enough protein.
- Causes a larger drop in movement such as NEAT and NEPA and a larger drop in resting metabolic rate.
- Increases potential for disappointment. If people don’t set up their crash diet correctly and they don’t see the results they want, they often give up and assume that no diet will work.
- Diminishes long-term habits to stay lean.
Medium Calorie Deficit = 15-25% Below Maintenance
- Provides strong, immediate, sustainable gratification. Decent and motivating rate of fat loss, often around 1-2 pounds per week.
- Causes some hunger, but usually manageable.
- Gives you more food choices, still room for treats and less nutrient dense foods.
- Usually causes training progress to decrease or stall, but rarely to regress. Recovery from workouts is usually slower, but not horrible.
- Allows you to keep training, so you can create a deficit through diet and exercise.
- Reduces risk of muscle loss for overweight or average people.
- Causes fewer instances of mood issues, lethargy, and metabolic slowdown.
- Increases risk of muscle and strength loss for lean people despite strength training and adequate protein intake.
- Elevates risk of decreased performance too much for high level athletes.
- Viewed as boring, since this is how most people diet.
- Slows fat loss compared to large deficits.
- Reduces margin of error when restricting calories. Easier to sabotage if you are bad at counting calories or get bored with your diet.
- Intimidates some people.
Small Calorie Deficit = <15% Below Maintenance
- Makes dieting easier. Reduces number of lifestyle changes needed. Often as simple as giving up soda or moving a little more throughout the day, like using a standing workstation.
- Lowers hunger to almost nonexistent levels (for many).
- Lower barrier to entry for people who are anxious about dieting. Easy to get the ball-rolling.
- Reduces lethargy, mood problems, or decreases in activity levels or metabolic rate.
- Reduces the risk of decreasing performance or recovery. Training might be slightly harder, but you can still maintain your intensity and volume.
- Drastically reduces the risk of muscle loss for lean people. You can sometimes completely prevent muscle loss if you also lift weights and eat enough protein.
- May increase long-term adherence if you are patient and consistent.
- Drastically reduces rate of fat loss. You have to diet longer and you often don’t notice any change in your appearance or weight for weeks.
- Requires more patience and consistency.
- Lowers your margin of error for food intake. You have to be very diligent about making sure you’re in a caloric deficit. If you eat even a few hundred calories more than you think, you won’t lose fat.
- These are all great options depending on the context. However, in the real world you’ll rarely need to stick perfectly to any of these approaches.
Why Not All Three?
- You don’t need to use the same deficit for your entire diet.
- Here are a few ways you could use different approaches to reach your goals:
- Start with a larger deficit and move toward a smaller deficit.
- Start with a smaller deficit and move toward a larger deficit.
- Plan periods where you eat a large deficit and periods where you eat a small deficit.
- Have some days where you’re in a much larger deficit and other days with less severe deficits.
- Use whatever size deficit suits your lifestyle at the time. Busy and less time to eat? Use a larger deficit. Holidays with lots of food? Use a smaller deficit.
How to Decide Which Deficit is Right For You
Look at the chart below to get an idea of which deficit is appropriate for your goals.
Keep in mind that there’s no reason you need to stick to these exact percentages — they’re ballpark estimates to get you started. The exact size of your deficit is something you’ll need to figure out for yourself or with a coach over time.
The Art of Selecting the Right Deficit
Deciding what calorie deficit you use to lose fat is not always easy. There are a lot of factors to consider, all of which depend on your goals, tolerances, and preferences. A deficit that’s perfect for one person might be totally inappropriate for another.
Cutting calories too much often creates more problems than it solves, but small deficits have their own downsides. With a little planning and experimentation, however, you’ll find a deficit that works for you.
Interested in a customized nutrition plan that’s continually adjusted to suit your goals? Check out our nutrition coaching options.
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