Will the Sardine Diet Help You Lose Weight?

Sardines are having a moment. Once relegated to the back of the pantry as a last-resort option, they’re now trending across social feeds. With that buzz comes the so-called “sardine diet.” Does it actually help with weight loss? Experts explain what it is and what it isn’t.

Like many weight-loss tips online, this one is a mixed bag. The bottom line first: eating a diet that’s 100% sardines isn’t a good idea. Despite the success stories doing the rounds, an all-sardine plan won’t support long-term weight management and will leave gaps in key nutrients. The good news is sardines do offer health benefits and can fit easily into a balanced diet.

Before stocking up, here’s what to know about these briny little fish—why a sardine-only plan falls short and how to include sardines sensibly as part of an overall healthy way of eating.

What is the sardine diet?

The sardine diet is a short-term plan built almost entirely around eating sardines. It was popularised online as a three-day challenge, though some people attempt it for longer. Typical advice includes drinking water or black coffee and using carb-free seasonings if the taste is hard to tolerate.

The trend has spread across social media, with anecdotal reports claiming notable short-term weight loss. Some stories describe losses of about 11 kg over four months or around 2 kg in three days. These accounts are self-reported and do not replace clinical evidence.

Does the sardine diet work for weight loss?

Despite the anecdotes, experts do not recommend the sardine diet for weight loss. “Eating only sardines might help you lose weight because you’ll likely get tired of the monotony and end up eating fewer kilojoules, but that’s just undereating, not the healthy weight loss we recommend,” explains bariatric surgeon Dr Hector Perez. “I see this pattern often in clinic, where extreme single-food diets result in short-lived weight loss, only to lead to deficiencies or backfiring when patients give up and binge-eat their favourite foods all of a sudden.”

Beyond being ineffective, relying on one item or category of food is not good for the body, says registered dietitian nutritionist Monica Auslander Moreno. “This can lead to dangerous nutrient deficiencies and electrolyte alterations,” she explains.

Sardine nutrition facts

A standard 106 g of sardines canned in spring water, drained, provides roughly:

• 795 kilojoules
• 22.6 grams of protein
• 351 milligrams of calcium
• 2 grams of fat
• 343% of the daily value (DV) for vitamin B12
• 22% DV vitamin D
• 15% DV iron

If packed in oil, the same serve typically contains 920–1,050 kJ and 12–14 grams of fat.

Sardines also supply zinc and magnesium and are naturally rich in omega-3 fatty acids (EPA + DHA), which support heart, brain and eye health and help temper inflammation.

Are sardines good for you?

Yes. While an all-sardine diet is not recommended, sardines can absolutely be part of a nutritious eating pattern.

“They are a low mercury fish as their small size renders them largely non-predatory and unable to build up much mercury in their tissues,” says Moreno. “They’re also affordable, easy to prepare—open can, insert fish into mouth!—and they are a high volume omega-3 fatty acid fish. This is linked to favourable benefits for immunity, cognition and a host of anti-inflammatory benefits. They’re also high in protein and contribute to satiety and muscle protein synthesis.”

Previous reporting has also noted that sardines packed with bones provide highly bioavailable calcium plus vitamin D, which supports absorption, making them a smart choice for bone health.

Risks of the sardine diet

Sardines are not high in fibre and your gut microbiome relies on fibre to support metabolism and hunger regulation. “You also risk too much sodium and an imbalance of vitamins and minerals,” says Perez. “I often see the consequences of overly restrictive diets in my practice: People lose weight quickly, but their metabolism, digestion and hunger cues end up worse than before.”

“Individuals with hypertension, kidney disease, heart failure, gout or sodium-sensitive conditions should avoid a sardine-only diet,” says physician Dr Rasoul Montazeri. “The sodium and purine load can worsen blood pressure, strain kidney function and trigger joint inflammation. Pregnant individuals or people with metabolic disorders also require a more balanced nutrient profile to remain healthy.”

Some tinned sardines contain small bones, which can be a choking hazard for anyone with swallowing difficulties. People with fish allergies should avoid sardines altogether.

If you are considering major dietary changes, speak with your GP or an accredited practising dietitian to build a balanced plan that meets your nutrient needs.

Does the sardine diet help you lose weight?

Short term, weight loss can happen on a sardine-only diet because intake drops. Long term, it’s not recommended. An all-sardine plan is low in fibre and misses key nutrients, can be high in sodium and is hard to sustain.

For healthy, maintainable weight loss, choose a balanced pattern such as the Mediterranean diet, the DASH diet or structured time-restricted eating. Sardines can fit well within these approaches thanks to protein and omega-3s, but they should be one part of a varied plate alongside vegetables, whole grains and other protein sources.

If weight management is the goal, pair an evidence-based eating plan with regular movement, good sleep and stress management and speak with your GP or an accredited practising dietitian for personalised guidance.