40-30-30 Diet Guide

Certified Nutrition Coach Explains the Pros & Cons

By: Jeremy Fox, CNC, CPTPublished: August 17, 2022

With all the information available today, it’s hard to know what diet advice to follow. Each new fad diet seems to insist on avoiding or eliminating something different.

On the other hand, the 40-30-30 diet is a more balanced approach to nutrition. And it doesn’t require as much elimination or sacrifice to improve your health and fitness.

So what is the 40-30-30 diet, and how do you know if it’s right for you? This article answers those questions and more so you can right for your body and lifestyle.

40-30-30 Diet

What is the 40-30-30 Diet Plan?

The 40-30-30 diet is a macronutrient-based approach to nutrition popularized by the Zone Diet program. American biochemist Barry Sears developed the Zone Diet in the late 1980s to combat “diet-induced inflammation.”

The basic principle of the 40-30-30 diet is that 40% of your calories come from carbs, 30% from protein, and 30% from fat. This macronutrient ratio is slightly lower in carbs and significantly higher in protein than the standard American diet (50-15-35)1.

40 30 30 Diet Macros

The Problem with High Carb Diets

The main issue with the high-carb Western diet is that it causes insulin resistance and type 2 diabetes. Insulin resistance is a hormone imbalance where your body can’t control blood sugar. And eventually, it can lead to type 2 diabetes, which is chronically elevated blood sugar.

Reducing carbs and increasing protein is an easy step toward reversing insulin resistance and preventing type 2 diabetes. In addition, it could help you maintain lean muscle while losing weight.

Science Behind 40-30-30 Diet

Scientific studies do not support all of the health claims made by Sears. For example, there is no evidence that this diet reduces inflammation or improves physical performance2.

However, some of the 40-30-30 diet concepts are based on sound science. And it could help improve your health and body composition in certain situations.

40-30-30 Diet Blood Sugar Control

The 40-30-30 diet appears to have a modest impact on blood sugar or insulin levels. And researchers suggest that such a diet could help control blood glucose in people with type 2 diabetes3.

The reason is that the reduced carbs and increased protein resulted in decreased 24-hour glucose concentration compared to a high carb, low protein diet. In addition, reducing starchy carb sources in favor of fibrous vegetables also played a role in blood sugar control.

40-30-30 Diet Blood Sugar

24-hour glucose levels were 35% lower on the 40-30-30 diet compared to a 55-15-30 diet among subjects with type 2 diabetes. Adapted from Gannon et. al.

40-30-30 Diet Weight Loss

The 40-30-30 diet results in eating about 60 grams less carbs per day compared to the standard western diet. And most studies show that this minor macronutrient shift does not have a significant effect on weight loss when calorie intake is the same between diets4.

However, the 40-30-30 diet also means you eat about 60 grams more protein per day. And those studies show that higher protein results in more fat loss and less muscle loss compared to the control diet. Although, the preservation of lean mass was more pronounced in women than men5.

40-30-30 Diet Weight Loss

The ratio of fat loss to muscle loss between a 40-30-30 diet and a 55-15-30 diet. A higher number means more fat and less muscle loss. Adapted from Layman et. al.

40-30-30 Diet Pros & Cons

So far, we’ve mostly talked about the health benefits of the 40-30-30 diet, like improving insulin sensitivity and preserving lean muscle. And there are other benefits, such as more flexibility compared to low-carb diets.

However, the 40-30-30 diet has downsides as well. Most notably, the Zone Diet recommends 1,200 calories daily for women and 1,500 calories for men. That makes it a very low-calorie diet and could result in significant muscle loss and metabolic damage in some individuals.

In addition, this diet plan requires you to understand and count macros, which may be more work than some are willing to do. Lastly, the 40% carb target isn’t tailored to your individual activity level, body, or fitness goals.


  • Easy to follow concept
  • Relatively flexible food choices
  • Well balanced nutrient intake
  • High protein supports lean muscle
  • Don’t have to eliminate carbs
  • May improve blood sugar control in people with type 2 diabetes


  • Does not prescribe a personalized calorie target
  • Requires knowledge of macronutrients in food
  • Must count macros
  • May be too many carbs for sedentary people
  • May be too few carbs for highly active people
  • Not tailored to your body or lifestyle
  • Beneficial effects are not as pronounced in men or those with healthy blood sugar levels

Related: Nutritionist Critiques the 90-30-50 Diet

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40-30-30 Diet Guidelines

The foundation of the 40-30-30 diet is the macronutrient ratio of 40% carbs, 30% protein, and 30% fat. And you could hit these targets with any food, like an IIFYM meal plan.

However, the Zone Diet prescribes certain foods to enhance blood sugar control and weight loss. Here are the general guidelines for following this diet to a T.

  • 40% Carbs: About 2/3 of each meal should consist of fibrous veggies and a little fruit. Avoid starchy carbohydrates like potatoes and corn.
  • 30% Protein: Roughly 1/3 of each meal should consist of lean protein from fish, eggs, poultry, beef, or low-fat dairy.
  • 30% Fat: The remaining 1/3 of each meal should consist of monosaturated fat like olive oil, avocado, or almonds.

40-30-30 Macro Meal Plan Example

At this point, you might like the idea of the 40-30-30 diet but don’t know where to start. So let me walk you through an example of how to find your macros for this meal plan.

For this example, let’s say that you need to eat 2,000 calories per day to progress towards your fitness goals. All you need to do from here is multiply 2,000 by the various macro percentages.

Remember, you can divide a percentage by 100 to make it a decimal with which you can multiply. So your 40% carb intake would be 2,000 x 0.4 = 800 calories. Protein and fat are 2,000 x 0.3 = 600 calories each.

Now to convert from calories to grams. Carbs and protein have 4 calories per gram, while fat has 9 calories per gram. So we divide the calories by these numbers.

That’s 800 ÷ 4 = 200 grams of carbs. 600 ÷ 4 = 150 grams of protein. And 600 ÷ 9 = 67 grams of fat.

Table 1. Example 40-30-30 Macros for 2,000 Calorie Diet

Macronutrient Calories Grams
Carbs (40%) 800 200
Protein (30%) 600 150
Fat (30%) 600 67

Simple enough, right? But if you don’t have a calculator handy or just don’t feel like messing with numbers, here’s a simple tool you can use to find your 40-30-30 macros.

40-30-30 Diet Calculator

Enter your actual daily calorie intake to see your 40-30-30 macro targets in grams.

40-30-30 Diet FAQ

Next, I’ll answer some of the most common questions surrounding the 40-30-30 diet.

Is 40-30-30 a good macro ratio?

In general, 40% carbs, 30% protein, and 30% fat is a decent starting point for people just getting into counting macros. And it represents a significant improvement over the high carb, low protein diet most people follow.

That said, there is no single best macronutrient ratio for everybody. And the 40-30-30 diet might not be ideal for your body or circumstances.

What foods can you eat on the 40-30-30 diet?

You can follow the 40-30-30 diet by eating any foods that result in hitting the macro targets at the end of the day. But, of course, you’ll get better results if you stick with mostly healthy, whole foods.

On the strict version of the 40-30-30 diet (Zone Diet), no food is technically off limits. But it encourages you to avoid eating starchy carbs and replace them with vegetables instead.

Here is a list of foods recommended on the Zone Diet.


  • Fibrous veggies like lettuce, broccoli, peppers, tomatoes, mushrooms, squash, onions, and more
  • Low-glycemic fruits like berries, apples, plums, and more
  • Grains like oatmeal and barley


  • Lean red meats like beef, lamb, and wild game
  • Poultry like chicken and turkey
  • Fish and shellfish
  • Egg whites
  • Low fat milk, cheese, and yogurt


  • Oils like olive, canola, and sesame
  • Nuts like peanuts, cashews, almonds, or pepitas
  • Nut butters
  • Avocados

What are the negatives of the 40-30-30 diet?

The biggest oversight of the 40-30-30 diet is that it doesn’t really tell you how many calories to eat. And your overall energy balance is more important than macronutrient ratios for losing weight or gaining weight.

So you might not make any progress toward your fitness goal unless you first calculate your ideal calorie deficit or calorie surplus.

Can you eat carbs and still lose belly fat?

Yes, you can eat carbs and lose belly fat if you’re in a calorie deficit! The idea that you must use extreme low carb or keto diets to get lean is a myth.

A balanced diet works just as well for burning fat and provides more variety. The key is not overdoing it with high-glycemic carbs or added sugars and consuming plenty of protein with your carbs.

Is 40 percent carbs too much?

Your ideal carb intake depends on your situation. For example, if you’ve been following the standard American high carb diet of 50-55% carbs, then 40% carbs can be a big improvement.

However, if you lead an inactive lifestyle and want to lose weight, 40% carbs could be more than you need. Conversely, 40% carbs might not be enough if you are extremely active and trying to gain or maintain muscle.

What is the best macro ratio to lose weight?

The best macro ratio depends on your body, activity level, and fitness goals. For optimal results, you should adjust your carb intake up or down based on these factors and ensure you get enough protein to support lean muscle.

Best Macros for Weight Loss

The 40-30-30 diet can work very well for some people trying to lose weight, especially if you’re new to reducing carbs or working out.

However, this is not the best macro ratio for every person or even for different days in your existing routine. Your ideal macros for weight loss should change with your body and schedule.

Click here for more detailed instructions on calculating your macros for weight loss.

Now that you’re an expert on the 40-30-30 diet check out some of my other informative articles on nutrition, workouts, and supplements!

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