Fish over meat: Why a pescatarian diet may help people with obesity live longer

If you are a non-vegetarian, eating fish might have more benefits than eating meat and poultry in clinical obesity.

A large UK study has found that people with clinical obesity who followed a pescatarian diet or fish-based diet lived longer than regular meat-eaters, or even those having a vegetarian diet.

But experts say the findings should not be interpreted as a reason for vegetarians to switch to fish, particularly in countries like India where dietary patterns and obesity differ significantly.

As obesity keeps fueling an increase in diabetes, heart disease and fatty liver disease across the world, one question is at the centre of scientific debate: Is it simply eating less meat that matters, or does the type of diet make the difference?

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A new study published in Nutrition Journal, Dietary patterns and mortality in clinical obesity: comparative risks of meat-based, pescatarian, and vegetarian diets offers a surprising answer. Among nearly 155,000 adults with clinical obesity followed for more than 16 years, those who ate a pescatarian diet — rich in plant foods but including fish while avoiding meat —had significantly better survival than regular meat-eaters. Surprisingly, the same benefit was not observed among vegetarians and vegans.

The findings challenge the assumption that all plant-based diets are equally protective and suggest that diet quality may matter more than simply avoiding meat.

A first look at diet using the new definition of obesity

The study analysed data from 154,986 UK Biobank participants who met the newly proposed definition of clinical obesity, introduced by The Lancet Diabetes & Endocrinology Commission in 2025. Unlike the traditional reliance on body mass index (BMI), the new definition identifies obesity as a disease when excess body fat causes organ dysfunction or health complications.

Researchers divided participants into four dietary groups—regular meat-eaters, occasional meat-eaters, pescatarians and vegetarians/vegans—and tracked deaths from all causes as well as premature deaths before the age of 70.

The differences were striking.

All-cause mortality was 12.75 percent among regular meat-eaters compared with 7.58 percent among pescatarians. Even after adjusting for age, smoking, alcohol use, physical activity, income, and education, pescatarians had significantly longer survival and a lower risk of premature death than regular meat-eaters.

Vegetarians and vegans, however, did not experience a statistically significant reduction in mortality after these adjustments. While the premature mortality rate was around 4 percent for those who had regular meat, occasional meat, and a vegetarian diet, and around 3 percent in pescatarians.

Why fish — but not necessarily vegetarian diets?

The researchers believe the answer may lie not in what people avoid eating but in what they actually consume.

Fish provides high-quality protein and omega-3 fatty acids that have long been associated with lower cardiovascular risk. At the same time, pescatarian diets generally contain less red and processed meat while maintaining good nutritional balance.

The vegetarian category in the study was broad, as it included people following very different eating patterns. Some consumed diets which were rich in vegetables, legumes, and whole grains, while others relied on refined carbohydrates and processed vegetarian foods.

Because the study did not assess overall diet quality or the consumption of ultra-processed foods, researchers caution that simply eliminating meat may not be enough if the replacement foods are nutritionally poor. heavily

What does this mean for India?

These findings are very relevant for India, where obesity is rising rapidly alongside diabetes and cardiovascular disease. But experts caution against drawing simplistic conclusions.

“A pescatarian diet is mainly plant-based but includes fish and seafood while excluding meat such as chicken, mutton and pork. This study suggests that among people with obesity, pescatarians had better survival than regular meat-eaters. However, these findings should be interpreted cautiously in India because dietary habits and the obesity profile of Asian Indians differ from those in Western populations,” said Dr Anoop Misra, chairman of Fortis-C-DOC Hospital for Diabetes and Allied Sciences.

He stressed that the study does not mean vegetarians should start eating fish.

“A well-planned vegetarian diet with adequate protein from pulses, soy, milk and nuts can also be healthy. Overall, diet quality, adequate protein intake, physical activity and weight management remain more important than the dietary label itself,” Dr Misra said.

In India, vegetarian diets are often rich in refined cereals such as polished rice and refined wheat flour, yet protein-deficient. Nutrition experts have increasingly warned that diets can be vegetarian yet unhealthy if dominated by refined and sugary foods and ultra-processed products.

Men appeared to benefit more.

Another notable finding was that the survival advantage associated with a pescatarian diet was more pronounced in men, particularly for premature mortality. Researchers suggest this could reflect biological differences in fat distribution and metabolic risk, since men are more likely to accumulate harmful visceral fat around abdominal organs.

However, they warn that the mechanisms remain uncertain and call for further research.

Not the final word

Despite its large sample size and long follow-up, the study has important limitations.

Diet was recorded only once at the start of the study, meaning researchers could not account for dietary changes over time. The analysis also lacked detailed information on nutrient intake, protein quality, and ultra-processed food consumption. Moreover, because the study population consisted largely of White adults in the UK, the findings cannot automatically be applied to Asian populations.