Is tuna good for weight loss?

Nobody has tested it. We found no randomized trial and no systematic review of tuna and body weight. The nearest evidence is fish as a whole. A 2023 network meta-analysis of 152 randomized trials in 9,669 adults found that eating more fish gave 1.9 lb (0.85 kg) of weight loss against control (95% credible interval 0.02 to 1.66), which the reviewers called trivial and rated low certainty. In people with overweight or obesity, no food group in that review gave important weight loss.

Unsettled. Everything below is borrowed from other fish, from fish oil, or from one single-meal test. Whether tuna behaves like cod inside a diet is a reasonable guess that no trial has checked.

What the trials found

Fish as a food group

The 2023 network meta-analysis judged fish against a threshold of 8.6 lb (3.9 kg), the smallest change it counted as mattering to patients. Fish came in well below it. An older meta-analysis of randomized trials, from 2014, mixed fish with fish oil and found 1.3 lb (0.59 kg) more weight lost than in controls (95% CI 0.21 to 0.96), with waist 0.32 in (0.81 cm) smaller. It did not find a difference in fat mass or lean mass.

Myth. Fish oil capsules do not make you lose weight. A 2015 meta-analysis of 21 placebo-controlled trials in adults with overweight or obesity found no effect on body weight (standardized difference -0.07, 95% CI -0.21 to 0.07) or BMI, with or without lifestyle changes. Waist-hip ratio did fall.

Lean fish inside a calorie cut

The trials that come closest to a tuna diet used cod, another lean fish, inside diets that already cut calories. In an 8-week trial of 126 young overweight adults on a diet 30% below their energy needs, people who ate 5.3 oz (150 g) of cod five times a week lost 3.7 lb (1.7 kg) more than people on the same diet without seafood. The reason was not worked out.

In an 8-week trial of 324 young overweight adults in Iceland, Spain and Ireland, three 150 g fish meals a week, or fish oil, were added to a calorie-cut diet. At 4 weeks the average man lost 7.8 lb (3.55 kg) on the control diet, 9.6 lb (4.35 kg) with cod, 9.9 lb (4.50 kg) with salmon and 11 lb (4.96 kg) with fish oil. In women the diets did not differ.

The longest trial pulls the other way. In 118 obese Australian adults followed for 12 months on a low-calorie diet, advice to eat two fish meals a week (180 g of fatty fish) did not add weight loss. The control group lost 9.9 lb (4.5 kg) and the fish group 9.5 lb (4.3 kg), with no significant difference. That trial gave advice and did not hand out fish.

The one trial with tuna

In a randomized crossover trial, 22 lean healthy men drank liquid meals made with whey, tuna, turkey or egg protein and were offered a buffet 4 hours later. They ate less after whey than after tuna, egg or turkey (P below 0.001), and reported less hunger after whey than after tuna. One drink in lean men says nothing about body weight over weeks. It gives no sign that tuna protein is unusually filling.

Where tuna can help

What tuna does offer a calorie-cut diet is a lot of protein for few calories. In UK composition data, 3.5 oz (100 g) of drained tuna canned in brine has 109 calories and 24.9 g of protein. The same amount canned in sunflower oil has 159 calories and 25.4 g of protein, and the extra energy comes from the oil. That is a fact about the food. It is not a trial result about weight.

For the rest of what tuna offers, see the tuna page and the canned tuna page.

Who should be careful

Not for everyone. A diet built around tuna every day runs into the mercury advice. US FDA and EPA guidance puts canned light tuna among Best Choices at 2 to 3 servings a week, and notes that albacore, also sold as white tuna, typically has three times more mercury than canned light tuna. That advice is written for people who are or might become pregnant, who are breastfeeding, and for parents of young children.

For those groups, see our review of tuna in pregnancy. Salt is the other number. In UK composition data, canning raises sodium from 66 mg per 100 g in raw tuna to 293 mg in brine and 368 mg in oil. Those figures come from different samples and possibly different species, so treat them as a rough guide. People limiting salt should check the label.

What expert bodies say

We found no expert body that addresses tuna and weight loss. The only official advice that applies to eating tuna often is the FDA and EPA guidance on mercury above, dated 2022.

How we searched

What would change this answer

• A randomized trial that adds tuna to a calorie-cut diet against the same diet with another protein, lasting months and measuring weight. We found none, finished or registered.
• A longer repeat of the cod trials. The two that found a benefit ran 8 weeks in young adults, and the one that ran 12 months found nothing.
• A satiety trial with tuna eaten as a solid meal, the way people actually eat it, in people trying to lose weight.

Sources

1. ev-tunwl-01 · Meta-analysis or systematic review · systematic review and Bayesian network meta-analysis of randomized controlled trials, GRADE · n = 9669
   Increased consumption of fish (MD - 0.85 kg, 95% CrI - 1.66, - 0.02; GRADE = low), whole grains (MD - 0.44 kg, 95% CrI - 0.88, 0.0; GRADE = very low), and nuts (MD - 0.37 kg, 95% CI - 0.72, - 0.01; GRADE = low) demonstrated trivial weight loss, well below minimal clinically important threshold (3.9 kg), when compared with the control group.
   
   Who: Adults in 152 RCTs comparing food groups or a food group against usual diet
   Effect: fish MD -1.9 lb (-0.85 kg) (95% CrI -1.66 to -0.02), GRADE low; below the 8.6 lb (3.9 kg) minimal clinically important threshold
   Certainty: The widest synthesis; tuna not singled out, this is all fish. In people with overweight there is no important effect.
   Eur J Nutr, 2023 · checked 2026-10-07 · we read the abstract
2. ev-tunwl-02 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = —
   We found evidence that participants taking fish or fish oil lost 0.59 kg more body weight than controls (95% confidence interval [CI]: -0.96 to -0.21).
   
   Who: Participants in randomized controlled trials of fish or fish oil intake
   Effect: weight -1.3 lb (95% CI -2.1 to -0.46; metric: -0.59 kg, -0.96 to -0.21); BMI -0.24 kg/m2; body fat -0.49%; waist -0.32 in (-0.81 cm); no difference in fat mass or lean mass
   Certainty: Fish and fish oil mixed; number of studies not given in the abstract.
   Obes Rev, 2014 · checked 2026-10-07 · we read the abstract
3. ev-tunwl-03 · Meta-analysis or systematic review · meta-analysis of randomized placebo-controlled trials · n = 21 studies
   Calculated results of the meta-analysis demonstrated that fish oil had no effect on reducing body weight (overall SMD = -0.07, 95% CI -0.21 to 0.07, P = 0.31) and BMI (overall SMD = -0.09, 95% CI -0.22 to 0.03, P = 0.14) whether alone or combined with life modification intervention in overweight/obese subjects.
   
   Who: Overweight/obese adults in 21 randomized placebo-controlled trials, 30 study arms
   Effect: body weight SMD -0.07 (95% CI -0.21 to 0.07); BMI SMD -0.09 (-0.22 to 0.03); WHR SMD -0.52
   Certainty: About capsules, not fish; shows that omega-3 as such does not reduce weight. Canned light tuna has little omega-3.
   PLoS One, 2015 · checked 2026-10-07 · we read the abstract
4. ev-tunwl-04 · Randomized controlled trial(s) · 8-week randomized controlled trial, energy-restricted diets · n = 324
   The diets did not differ in their effect on weight loss in women.
   
   Who: 324 men and women aged 20-40 years, BMI 27.5-32.5, Iceland, Spain and Ireland; 3 x 150 g fish per week
   Effect: average man at 4 weeks: control -7.8 lb (-3.55 kg), cod -9.6 lb (-4.35 kg), salmon -9.9 lb (-4.50 kg), fish oil -11 lb (-4.96 kg); no difference in women
   Certainty: Fish within limited calories, not in addition. No tuna; cod is the closest analog of lean tuna.
   Int J Obes (Lond), 2007 · checked 2026-10-07 · we read the abstract
5. ev-tunwl-05 · Randomized controlled trial(s) · 8-week randomized controlled trial · n = 126
   According to linear models weight loss was 1.7 kg greater among subjects consuming 150 g 5x/week compared to the control group (P<0.015).
   
   Who: 126 subjects aged 20-40 years, BMI 27.5-32.5, energy-restricted diets (-30%)
   Effect: +3.7 lb (1.7 kg) weight loss with 5 x 150 g cod/week vs no seafood (P < 0.015); dose-response P < 0.001
   Certainty: Lean fish, isocaloric diet; mechanism not clarified. 8 weeks.
   Nutr Metab Cardiovasc Dis, 2009 · checked 2026-10-07 · we read the abstract
6. ev-tunwl-06 · Randomized controlled trial(s) · 12-month parallel randomized placebo-controlled trial · n = 118
   Advice to consume 2 fish meals per week did not enhance the effects on weight loss of a healthy low calorie diet.
   
   Who: 118 obese Australian adults, mean BMI 31.3, mean age 45, 28% male; 2 servings (180 g) fatty fish per week
   Effect: 12 months: control -9.9 lb (-4.5 kg), fish -9.5 lb (-4.3 kg), fish + LCn3PUFA -7.3 lb (-3.3 kg); no significant difference between groups
   Certainty: The longest RCT; advice, not fish provided. Contradicts the short cod RCTs.
   BMC Public Health, 2013 · checked 2026-10-07 · we read the abstract
7. ev-tunwl-07 · Randomized controlled trial(s) · single-blind randomized crossover trial, acute · n = 22
   Mean energy intake at the ad libitum meal was significantly lower (P < 0.001) with the whey meal than with the tuna, egg and turkey meals.
   
   Who: 22 lean, healthy men; liquid test meals of whey, tuna, turkey or egg albumin; buffet 4 h later
   Effect: ad libitum energy intake lower after whey than after tuna, egg and turkey (P < 0.001); hunger AUC lower after whey than tuna (P < 0.033)
   Certainty: The only study specifically with tuna; single serving, liquid meal, lean men. It says nothing about weight.
   Br J Nutr, 2010 · checked 2026-10-07 · we read the abstract
8. ev-tunwl-08 · Position of an expert body · food composition dataset · n = 2 records
   Tuna, canned in brine, drained (16-416): Energy 109 kcal, Fat 1.0 g, Protein 24.9 g || Tuna, canned in sunflower oil, drained (16-417): Energy 159 kcal, Fat 6.4 g, Protein 25.4 g
   
   Who: CoFID 2021 Tuna, canned in brine, drained (16-416); canned in sunflower oil, drained (16-417)
   Effect: per 3.5 oz (100 g) brine / oil: energy 109 / 159 calories; protein 24.9 / 25.4 g; fat 1.0 / 6.4 g
   Certainty: The difference of 50 calories per 3.5 oz (100 g) is from oil. No quote, set and codes named.
   CoFID 2021 (Public Health England, OGL v3.0), codes 16-416, 16-417 Tuna · checked 2026-10-07 · we read the dataset
9. ev-tunwl-09 · Position of an expert body · agency consumer advice · n = -
   Canned light tuna is in the “Best Choices” category and it is fine to eat 2 to 3 servings per week. ... Albacore tuna, also known as white tuna, typically contains three times more mercury than canned light tuna.
   
   Who: People who are or might become pregnant, breastfeeding, and parents of young children
   Effect: canned light tuna: 2-3 servings per week; albacore (white) about 3x the mercury of canned light tuna
   Certainty: For the 'tuna every day' diet, the main caveat: mercury, especially albacore, pregnancy, and children. The page is dated 02/17/2022.
   FDA/EPA, Questions & Answers from the FDA/EPA Advice about Eating Fish, 2022 · checked 2026-10-07 · we read the section
10. cntu-daily-r5-02 · Position of an expert body · food composition dataset, raw versus canned · n = 3 records
    Tuna, flesh only, raw (16-399): Energy 107 kcal, Fat 0.7 g, Sodium 66 mg, Selenium 93 ug, Vitamin D 3.2 ug || Tuna, canned in brine, drained (16-416): Energy 109 kcal, Fat 1.0 g, Sodium 293 mg, Selenium 69 ug, Vitamin D 1.1 ug || Tuna, canned in sunflower oil, drained (16-417): Energy 159 kcal, Fat 6.4 g, Sodium 368 mg, Selenium 87 ug, Vitamin D 1.1 ug
    
    Who: CoFID 2021 Tuna, flesh only, raw (16-399); canned in brine, drained (16-416); canned in sunflower oil, drained (16-417)
    Effect: per 3.5 oz (100 g) raw / brine / oil: energy 107 / 109 / 159 calories; fat 0.7 / 1.0 / 6.4 g; sodium 66 / 293 / 368 mg; selenium 93 / 69 / 87 ug; vitamin D 3.2 / 1.1 / 1.1 ug
    Certainty: different samples and possibly different tuna species; not a retention factor
    CoFID 2021 (Public Health England, OGL v3.0), codes 16-399, 16-416, 16-417 Tuna · checked 2026-09-29 · we read the dataset