How Much Is Too Much and Is It Bad for You?

Can you eat too much protein? It’s one of the most common questions in every gym. Some people swear that more protein always means more muscle, while others warn that too much protein will make you fat or damage your kidneys. So who’s right?

Researchers have actually put this to the test. In a study published in the Journal of the International Society of Sports Nutrition, trained lifters increased their protein intake to about 3.4 grams per kg of body weight (around 1.5 g per lb) – far above what most people eat. The result? No extra muscle, but more fat loss and no signs of harm.

In this article we’ll look at how much protein you really need, what happens when you eat “too much protein”, what the research says, and who should actually be careful.

How Much Protein Do You Actually Need?

For people who lift weights, the International Society of Sports Nutrition recommends 1.4 to 2.0 grams of protein per kg of body weight per day (about 0.6 to 0.9 g per lb). That’s enough to build and maintain muscle mass for most lifters.

There are a couple of exceptions:

• When you’re cutting. Resistance-trained people on a calorie deficit may benefit from 2.3 to 3.1 g per kg, to help hold on to muscle while losing fat. Here’s more on how much protein you should eat to lose fat without losing muscle.
• Per meal. Around 20–40 grams of high-quality protein per meal (roughly 0.25 g per kg) works well for most people. Read more about how much protein your body can absorb in one meal.

So for an 80 kg (176 lb) lifter, that’s about 110–160 grams of protein a day. Want the full breakdown? Here’s how much protein you need to build muscle.

How Much Protein Is Too Much?

There’s no official “maximum” for healthy people, and that’s exactly why this question causes so much confusion. In studies on trained lifters, intakes of up to around 3.3–3.4 g per kg a day – roughly double the standard recommendation – haven’t caused any measurable harm over several months.

In practice, “too much protein” usually doesn’t mean dangerous. It means more than your body can use for building muscle. Once you go past about 2 g per kg, extra protein won’t give you extra muscle – your body simply burns the rest for energy. You’re not hurting yourself, but you’re not getting any bigger from it either. And you’re spending a lot of money on chicken breasts and protein powder.

What the Research Says About Eating Too Much Protein

It is common knowledge that bodybuilders build muscle optimally by eating around 1.5 to 2 g of protein per kg of body weight. But what will happen to your body if you double that and eat “too much protein”? Will you gain more fat? Will it have a negative impact on your health?

Researchers at Nova Southeastern University in Florida set out to answer exactly these questions.

The Study

The eight-week study included 48 healthy, resistance-trained men and women who already had years of weight training under their belts. They were divided into two groups. The first group kept their normal protein intake, while the second group was asked to increase it a lot, without making any other drastic changes to their diet. In other words, their intake of carbs and fats stayed about the same.

The subjects were free to choose their proteinents, while the rest ate more high protein foods. Both groups followed the same heavy resistance training program, five days a week

In the end, the normal protein group ate about 2.3 grams of protein per kg of body weight a day, while the high protein group ate about 3.4 grams per kg (1.5 g per lb). Since nothing else changed, the high protein group also ate around 400 more calories per day.

The Results

Interestingly enough, the extra protein had no effect on muscle growth. Both groups gained the same amount of lean mass – about 1.5 kg (3.3 lb) each.

But here’s the surprising part. Even though the high protein group ate about 400 more calories every day, they lost more fat: about 1.7 kg (3.7 lb) of fat, compared with just 0.3 kg (0.7 lb) in the normal protein group. Their body fat percentage dropped by about 2.4%. One likely explanation is that protein costs more energy to digest than carbs or fats, and a high protein diet may also increase how many calories you burn at rest.

Both groups also got stronger, with similar improvements in the squat, bench press, vertical jump and pull-ups. There was no meaningful difference between them.

The researchers also ran blood tests on some of the subjects, measuring blood sugar, electrolytes and kidney markers. They found no changes – no sign that eating that much protein was harmful.

Keep in mind that this was a relatively small study, and the high protein group happened to have more training experience. But the results line up with other research by the same team. In a follow-up crossover study, trained men ate around 2.6–3.3 g of protein per kg for four months, with no harmful changes in their blood lipids, kidney function or liver function.

Signs You’re Eating Too Much Protein

For healthy people, eating a lot of protein isn’t dangerous, but going overboard can still cause some annoying side effects:

• Digestive problems. Bloating, gas or constipation are common, especially if most of your protein comes from shakes and you’re not eating enough fiber. Some people also don’t handle large amounts of whey well because of the lactose.
• Feeling thirsty. Your body needs more water to process extra protein, so drink plenty of it.
• Low energy in the gym. If protein pushes most of the carbs out of your diet, your workouts can suffer. Carbs are still your main fuel for hard training.
• Bad breath. Very high protein, very low carb diets can put you into ketosis, which often comes with bad breath.
• Weight gain. Protein still has calories – 4 per gram. If extra protein pushes you into a big calorie surplus, you will gain weight, even if protein is less likely to be stored as fat than carbs or fats.
• Missing nutrients. If your plate is all meat and shakes, you’re probably missing out on the fiber, vitamins and minerals from fruits, vegetables and whole grains.

Is Too Much Protein Bad for Your Kidneys?

This is the biggest fear people have about high protein diets, and it’s one of the most common protein myths. In healthy people with normal kidney function, studies on high protein intakes – including the ones above – haven’t found any kidney damage.

It’s a different story if you already have kidney disease. Damaged kidneys have a harder time handling the waste products from protein, which is why people with kidney problems are usually told to limit their intake.

Who should be careful with high protein diets:

• People with kidney disease or reduced kidney function
• People with liver disease
• Anyone whose doctor has told them to limit protein

If you’re in any of these groups, talk to your doctor before increasing your protein intake.

How to Get Your Protein Intake Right

• Aim for 1.4–2.0 g per kg (0.6–0.9 g per lb) if you lift weights. That covers almost everyone.
• Go higher when you’re cutting. Up to 2.3–3.1 g per kg can help you keep muscle while you lose fat.
• Spread it out. Eat 20–40 g of protein in each of your 3–5 meals instead of loading it all into one or two.
• Choose whole foods first. Meat, fish, eggs, dairy and legumes, with shakes as a convenient top-up. Need ideas? Here’s how to get 200 grams of protein a day.
• Don’t forget carbs, fats and fiber. Protein builds the muscle, but you still need the other nutrients to fuel your training and stay healthy.
• Drink enough water, especially on a high protein diet.

Conclusion

So, can you eat too much protein? For healthy people, eating more protein than you need isn’t dangerous, and it won’t make you fat – the research actually shows the opposite. It just won’t make you any bigger either. About 1.4–2.0 g of protein per kg (0.6–0.9 g per lb) of body weight is enough for building muscle and strength for most lifters, and there’s no need to go much higher unless you’re dieting.

If you do have kidney or liver problems, though, be careful and talk to your doctor first. Interested in the opposite approach? Find out whether too much protein could actually limit your gains.