Over recent years, zero carb “carnivore diets” have rapidly grown in popularity.
There’s certainly no shortage of people claiming to enjoy the benefits of the zero carb lifestyle, and it even makes standard keto diets look carb-heavy.
But is a carnivore diet for humans healthy?
Is it ideal?
Or is it potentially dangerous?
This article takes a balanced look at the zero carb diet and the benefits, risks, and health impacts.
What is a Zero Carb Diet?
By its very nature, animal foods form the basis of the zero carb diet.
However, a zero carbohydrate diet plan can take several forms.
While some people concentrate on meat, others eat a wider variety of foods such as eggs, cheese, organ meats, and seafood.
The diet tends to be high in both fat and protein, and there are a wealth of success stories showing the important benefits the diet can have.
Specifically, zero carb dieters achieve significant results regarding weight loss, satiety, and better mental well-being.
On the other hand, there are many unknowns about the diet. In particular, potential long-term adverse effects are a concern for some.
Later on, this review will investigate both of these points in further detail.
What Foods Have No Carbs?
Some people follow the “eat meat, drink water” mantra and eat nothing other than steak and water.
Others consume a greater variety of foods from various types of meat to bacon, organ meats, eggs, cheese, and coconut oil.
It’s worth noting that not all these foods are actually zero carb—eggs come in at 1g carbohydrate—but they are close enough.
Here is a list of (nearly) zero carbohydrate foods;
- Coconut oil
- Fish (mackerel, trout, salmon, and sardines for omega-3)
- Olive oil
- Organ meats (heart, kidney, liver)
While all these foods are “allowable” on zero carb, some Carnivore diet proponents eat very little other than beef.
Is There a Historical Argument For Zero Carb?
With the explosion of the ancestral health scene over the past decade or so, the foods our ancestors ate is an evergreen topic of discussion.
On that note, think back to the prehistoric days and a caveman tucking into a slab of meat is a typical image.
And it’s accurate imagery too; as a species, humans have been eating meat for tens of thousands of years.
An interesting hypothesis worth reading is ‘The Carnivore Connection,’ which views carnivory as essential to recent human evolution.
In particular, the authors believe that (6);
- Low carbohydrate, high protein diets dominated the previous two million years of evolution.
- For a large amount of this time, dietary carbohydrate was scarce due to successive ice ages.
- Insulin resistance genes developed to give a survival advantage in response to lengthy low-carbohydrate periods.
But…Ancient Humans Ate Plant Food
Hunter-gatherers often lived through times of famine, and they ate what they could to survive.
Would they pass up some juicy berries they came across? Not likely.
Also, much of our modern evolution reportedly took place in Africa, a region with thousands of different species of vegetation.
Outside of the ice age periods, there would have been sufficient plant food available.
It’s highly unlikely people would pass this up, especially during times of hunger.
As a large source of energy, it’s certainly likely that ancient man valued meat more than plant foods.
However, this doesn’t mean plant foods played no part in the diet. Further, the majority of evidence indicates humans are natural omnivores and had different diets depending on their location and environment (7, 8, 9, 10).
Is Restricting Vegetables Dangerous?
A zero carb diet obviously involves cutting out vegetables.
Vegetables (especially greens) are very high in nutrient density, and the media constantly bombard us with messages about their health properties.
As a result, the majority of the health-conscious population would probably react in horror to the idea of restricting them.
But are vegetables really so necessary?
Vitamins and Minerals
First of all, we have to forget the myth that vitamins and minerals only come from plant foods.
They do not.
In fact, animal foods are some of the most nutrient-dense in the world.
To make it fair, the value is the RDA % per 100g;
As shown above, both animal foods and plant foods can contain high amounts of vitamins and minerals. Organ meats are especially nutritious.
Many people presume that zero carb diets are going to be severely deficient in many nutrients.
However, it is certainly possible to get most essential nutrients from eating a range of meat, seafood, eggs and organ meats.
On the other hand, antioxidant vitamins C and E are particularly difficult to obtain from animal foods.
Are Nutrient Deficiencies Important?
Many zero carb proponents point to accounts of people eating a meat-only diet for 15-20 years with no evidence of harm.
In addition, our biological need for certain nutrients drops as our carbohydrate intake lowers.
Despite this, we should remember that while anecdotes are always valuable and relevant, they are not evidence.
We can’t prove the long-term safety of zero carb simply because we don’t have sufficient research.
Also, chronic health problems typically develop over decades, so we can’t assume that 15-20 years of feeling great is predictive of the future.
This does not mean that a zero carb diet can’t be healthy in the long-run. It could well be, but it’s the responsible position to take since we don’t have much evidence now.
Polyphenols are biologically active compounds naturally found in plants, and particularly good sources include cacao, berries, olives and red wine.
Notably, numerous studies—including RCTs—show that consuming polyphenols alongside meals;
- Polyphenols from tea, herbs, and red wine can inhibit the formation of heterocyclic amines (HACs). These compounds are “likely carcinogens” and can occur when cooking meat at high temperatures or to a well-done stage (25, 26, 27).
What Are the Health Benefits of Zero Carb Diets?
As with any diet, there are several pros and cons of a carnivorous diet.
Firstly, zero carb diets have a range of health benefits.
In general, these are somewhat similar to the carbohydrate-restriction benefits of a ketogenic diet.
However, the effects are likely more powerful due to the further restriction of dietary carbs.
A typical zero carb diet should result in;
- More efficient weight loss: most people experience significant weight loss results; a reduced body fat percentage and losing weight around the waist is common. Additionally, carbohydrate restriction has a superior impact on weight loss and metabolic syndrome risk than low-fat diets do (28, 29, 30).
- Better mental wellbeing: very low carb diets tend to result in better cognitive performance, improved mood, focus, and mental clarity (31, 32).
- Reduction in food cravings: ultra-low carb diets massively improve satiety and reduce food cravings (33, 34).
- Decreased triglycerides, higher HDL: higher levels of dietary fat and lower levels of carbohydrate reliably increase HDL and reduce triglyceride levels (35, 36).
- Reduced blood glucose: restricting carbohydrate reduces and stabilizes fasting blood sugar levels (37).
- Less digestive issues: reducing carbohydrate tends to improve gas, bloating problems and heartburn. On this note, many people turn to the zero carb diet after unsuccessfully trying to resolve sometimes severe digestive issues.
The Bacon Experiment
Okay, we shouldn’t take this as evidence, but there was an interesting trial undertaken by one man.
What he did was…eat bacon.
For 30 days. Nothing else – just bacon!
- 20 pounds of weight loss
- Improved cardiovascular health markers
- Lower blood pressure
These results don’t prove or verify anything—and it’s not a diet I’d recommend—but it does upset the conventional fear of meat as some kind of “artery-clogging” food.
For those unaware, these health markers are likely the most protective against cardiovascular risk (38).
Are There Any Health Risks?
There don’t appear to be any immediate health risks from zero carb diets, other than typical keto flu style symptoms.
In my personal opinion, there’s no reason to suspect that zero carb dieters can’t enjoy long-term health.
However, there is also no evidence of long-term safety.
Is it Sustainable?
One of the biggest problems with all diets—whether vegan, paleo, keto or zero carb—is sustaining them.
Pizza delivery with friends? Well, that’s a difficult ask even for a strict paleo dieter.
This lifestyle struggle only multiples with zero carb, since the diet rules out almost all non-animal foods.
Eating no carbs at all certainly has an effect on social events.
For instance, occasions like birthdays, Christmas dinner, or a night out with friends or family become much tougher.
Do-able, certainly – but tougher.
On the positive side, zero carb foods such as bacon and beef are delicious and make the limited food choice easier.
And many people are sustaining the diet – both because they love the food and feel it is making them healthier.
Zero Carb: Healthy or Harmful?
Personally, I think that a zero carb diet is much healthier than the ultra-processed foods typical of standard Western diets.
I also believe that the diet is unlikely to be harmful – especially if well-formulated.
However, there is so much evidence for the health benefits of foods like cacao, berries, avocados, olives, and various other fruit and vegetables.
Sure, it might be possible to find a study or two about anti-nutrients in these foods, but the body of evidence points to them having substantial health benefits.
To sum up, I don’t think a zero carb diet is harmful.
But personally, I think a diet that includes a variety of nutrient-dense animal and plant foods is optimal.
For a closer look at two slightly higher carb diets, see this guide to keto vs paleo.