The Conscious Gut

Tuna And Water Diet: What Do Experts Say About Following It?

Tuna And Water Diet: Is It A Fast Solution Or A Health Hazard?

The tuna and water diet is one of those ‘get slim quick’ diet plans that every so often pops ups and gains popularity by promising to help the masses lose weight in the shortest time frame possible. However, before you get excited about fitting into your jeans in just a week or two, it is best to do a little due diligence on the topic. Does the tuna and water diet aid weight loss? Is the tuna and water diet safe and healthy? What do experts and science say about it?

It is no secret that weight loss can be a frustrating process. It takes time, dedication, and effort, something that many of us, more often than not, are not willing to do. When we decide to try it, many of us find that it is not as easy as we first anticipated, and it takes much longer than we thought it would. Thus, quick fixes like the tuna and water diet plan can seem like a good idea. After all, it is quick, cheap, and convenient.

What is the tuna and water diet?

This is a low-calorie, low-carbohydrate, high-protein diet that requires you to consume nothing but canned tuna and water for 3 consecutive days. This, however, is not a new diet. It has been around for many years and is more popular in bodybuilding circles.

This eating plan was created and popularized by the famous American award-winning bodybuilder and author, Dave Draper (7). According to Dave, the tuna and water diet bodybuilding benefits include fast fat loss and muscle gain, something that many bodybuilders do right before a competition.

How to follow the tuna and water diet

As stated above, to follow this diet, you are required to eat nothing but tuna and only drink water for three days. According to the creator of this eating plan, you should consume 2 to 4 liters of water a day and 1 to 1.5 grams of protein (tuna) per pound of body weight. The canned fish should only be soaked in either brine or water, not oil, mayonnaise, or vinegar, and neither should it have any spices.

190-pound man * 1.5 g protein = 285 g protein per day

285 g / 6 meals = 47.5 g protein per meal

He suggests that you should not consume all this protein in one sitting, but divide it into six equal portions that you shall consume throughout the day. You should also consume your fiber, vitamins, and minerals from oral supplements, not actual food for these 3 days.

Once the 3 days tuna and water diet is complete, you can now start eating more, but this food is limited to poultry, low-fat cottage cheese, and some salad or steamed vegetables. During this time, you are also required to continue working out. However, your exercises should only use moderate weights (8).

Tuna and water diet nutrition facts

A can of unsalted white tuna in water, but drained (172 g) has the following nutrition facts per serving (6):

  • Calories – 220
  • Carbohydrates – 0 g
  • Protein – 40.6  g
  • Fats – 5.1 g
  • Calcium – 24 mg
  • Iron – 1.7 mg
  • Magnesium – 57 mg
  • Phosphorus – 373 mg
  • Potassium – 408 mg
  • Sodium – 86 mg

Other variations of the tuna and water diet weight loss plan

Dave Draper’s eating plan is incredibly restrictive in terms of energy intake per day. When combined with exercise, it can be quite dangerous for anyone using it for fat loss. In light of this, people have come up with different variations of this eating plan over the years.

While still quite low in calories, these variations are more nutritious as they allow you to have more foods, not just canned tuna, and a jug of water. An example of this is the lemon water and tuna diet. This variation is touted as a way to enable you to lose weight, boost your metabolism, and build lean muscle mass.

This is what a typical day of the lemon water and tuna diet would look like:

Meal 1

Lemon water

1 cup of water, juice of half a lemon, and 1 tbsp honey

Calories: 21. Fats: 0 g. Proteins: 0 g. Carbs: 5.8 g

Meal 2

Eggs, milk, and fruit

100 g egg whites, 1 cup unsweetened almond milk, 1/2 cup pomegranate

Calories: 198. Fats: 3 g. Proteins: 8 g. Carbs: 28 g

Meal 3

Crackers and tea

2 multi-grain crackers, 1 cup oolong tea, 5 drops stevia

Calories: 70. Fats: 3 g. Proteins: 2 g. Carbs: 10 g


Meal 4

Tuna salad

1 can plain tuna, 1 tbsp mayonnaise, 1 small celery stalk, 1 tbsp chopped red onion, 1/2 tbsp cilantro/parsley, 1/2 tsp Dijon mustard, salt, and pepper to taste.

Calories: 228. Fats: 12 g. Proteins: 30 g. Carbs: 1 g

Meal 5

Green tea

1 cup of unsweetened green tea

Calories: 0. Fats: 0 g. Proteins: 0 g. Carbs: 0 g

Meal 6

Tuna salad wrap

1 whole-grain wrap, 1 can plain tuna, 1 tbsp mayonnaise, 1 small celery stalk, 1 tsp chopped red onion, 1/2 tbsp cilantro/parsley, 1/2 tsp Dijon mustard, salt, and pepper to taste.

Calories: 365. Fats: 16 g. Proteins: 34 g. Carbs: 21 g

Total intake for the Day: Calories: 882. Fats: 33 g. Proteins: 74 g. Carbs: 66 g

It is important to note that while lemon water is often believed to be  a weight loss secret, it  is actually a myth (3). Lemon water will not aid in weight loss. It may, however, aid your body in the following ways:

  1. Reduces inflammation;
  2. Protects the body’s cells from damage due to its antioxidants;
  3. Boosts immunity due to high Vitamin C levels;
  4. Helps treat kidney stones.

Another important fact to note is that this diet is extremely low in calories. Your recommended calorie intake is determined by multiple factors including age, gender, and level of physical activity. However, even without considering these very crucial factors, it is advisable that a daily calorie intake should not fall below 1,200 a day for women or 1,500 a day for men (4).

Does the tuna diet aid weight loss?

Yes, it technically does. However, is the tuna and water diet safe? No, it is not. Trying this eating plan for weight loss could come at a great risk to your health. The tuna and water diet is, at its core, nothing more than a crash diet. Crash diets are popular among people who want to lose weight fast; however, experts are firmly against them and rapid weight loss.

Such diets are not sustainable in the long run, and you will most likely gain all the weight back once you stop dieting. Some undesirable effects of crash dieting include (12):

  • Hunger
  • Fatigue
  • Irritability
  • Hair loss
  • Muscle cramps
  • Dizziness
  • Constipation or diarrhea
  • Dehydration
  • Menstrual irregularities

Severe and possibly life-threatening risks of crash diets include:

Nutrient deficiencies

Crash diets like the tuna and water diet are usually incredibly restrictive by asking you to cut out major food groups from your life. For instance, this eating plan and many other popular diets call for the exclusion of most carbohydrates. Others will exclude fats and dairy foods.

This is unhealthy because, for good health, human beings need a minimum amount of protein, fats, carbohydrates, vitamins, minerals etc. on a regular basis. This is hard to achieve on a crash diet that excludes the major food groups available.


These are formed in the gallbladder, a small organ under your liver. Some of the causes of gallstones include obesity, eating habits with regular consumption of fat and cholesterol-rich food, and rapid weight loss, which happens when you crash diet.

Loss of muscle  mass

When you are malnourished due to lack of nutritious food, your body starts to slowly break down your muscle to get the energy that it requires for you to function normally (9) and you start losing muscle mass.

Slow  metabolism

Losing weight too fast can cause your metabolism to slow down by up to 23%. This means that your body burns calories slower, which leads to weight gain. When food is not digested fast enough to be used as energy, your body turns it into fat and stores it within you.

Dangers of tuna and water diet for weight loss

Is eating only tuna healthy? No, it is not. Having two or three cans of tuna a day while drinking only  water is not healthy for anyone, and it is not something you should attempt doing on a day-to-day basis. Going further and incorporating exercise in your day makes the diet even more dangerous for you. As seen above, tuna is quite low in calories and water offers no macronutrients like carbohydrates, protein and fat.

Here is why you should not attempt this eating plan:

High risk of mercury poisoning

Tuna fish, fresh or canned, has more mercury than other popular types of fish and seafood. This is because, when alive, tuna fish feed on smaller fish, which are already contaminated with varying amounts of mercury.

This means that when you consume a lot of tuna, you are slowly increasing the amount of mercury in your system, leading to mercury poisoning over time. Some mercury poisoning symptoms include muscle weakness, nausea and vomiting, lack of motor skills, loss of sensation in the hands or face, changes in vision, hearing, or speech, and difficulty breathing.

Long-term effects of this are paralysis, neurological disorders, reduced sperm count or decreased fertility, and increased risk of heart problems (11). If you want to consume this fish, it is best to avoid subspecies such as albacore, yellowfin, and bigeye in favour of light or skipjack as they usually have a lower mercury content (10).

Nutrient deficiencies

Water has no calories and nutrients. Tuna, on the other hand, is rich in protein with very little amounts of fats and no carbs. Consuming only  these two macros does not provide you with all the nutrients you need to function properly.

Very limited in calories

Women should not eat less than 1200 calories a day, while men should not consume anything less than 1500 calories a day. The tuna diet previously mentioned does not even come up to 1000 calories, which puts you at a very low and dangerous caloric deficit.Very-low-calorie diets should only be done under medical supervision.

They are also reserved for obese or severely obese persons who are managing diabetes, going to have surgery, or preparing for fertility treatment (13). This is not a diet that should be used for weight loss or for building muscle.

Benefits of tuna and water diet bodybuilding

As we have seen so far, the tuna and water diet is not something that doctors and dietitians  would advise you to do whether you are trying to lose weight or build muscle. However, incorporating tuna and more water in your diet could help you manage your weight and build muscle.

Consuming tuna, and other types of oily fish such as salmon, cod, mackerel, halibut, trout, and snapper can aid in bodybuilding and weight loss because they are (2):

  • Low in calories

For weight loss, tuna and other fish are fantastic as you can consume a moderate amount of them without going over your calorie deficit. When on a bulk, they leave enough room  in your diet for more calorie-dense foods like legumes and whole grains.

  • Low in fat and high in Omega 3 fatty acids

These fatty acids can help fight anxiety and depression, improve eye health, reduce the risk of heart disease, and fight inflammation. Omega 3 may also help fight cancer and age-related mental health illnesses like Alzheimer’s (1).

  • High in protein

Protein is the building block of your muscles. Thus, eating adequate amounts of protein helps you maintain muscle mass and promotes muscle growth when you do strength training.

Water also keeps you hydrated, prevents water weight, and is a calorie-free drink. However, water and tuna should be consumed as part of a healthy diet, a diet that is within your recommended calorie intake, and incorporates all food groups. Consume whole grains, complex carbs, lean proteins, fruits, vegetables, and dark leafy greens.

The Bottom Line: Should you try the tuna and water diet?

No, you should not. This eating plan may promise and deliver quick weight loss results, but it is not worth it in the long run. Not only is it not sustainable, but it has numerous side effects, some of them being potentially life-threatening.

If you are looking to lose weight, It is best to cut your daily calorie intake  by 500 to 1000. This creates a deficit of 3500 to 7000 calories a week and will help you lose 1 to 2 pounds a week. It would also help if you tried working out for at least 30 minutes a day. You could just do bodyweight exercises or incorporate resistance and free weights.

If you are unsure how to make a healthy diet, please speak to a dietitian, and they can help you find the best way forward. Also, always remember to consult a doctor before making any dietary changes or starting a workout routine, especially if you have a chronic illness. Supplement your diet with some exercise to double your results.

Alexandra Danieli

Alexandra Danieli, CHC, The Conscious Gut
🥑 Overcome Anxiety and Depression
💩 Heal your Gut naturally

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