Some people believe that replacing meat with fish for protein during a diet is a good idea. This is because fish generally has a lower fat content, but it's important to be cautious as fish can sometimes be higher in calories than expected.

Among fish, mackerel and sardines, which are high in oil content, have higher calories than expected. According to the Food and Drug Administration's Food and Nutritional Content Database, based on a fish piece (100g), mackerel has 246 kcal, sardines 232 kcal, hairtail 149 kcal, bluefin tuna 132 kcal, anchovy 127 kcal, salmon 106 kcal, gizzard shad 107 kcal, cod 86 kcal, pollock 80 kcal, and monkfish 63 kcal. When seasoned or fried in oil, the calorie content increases further.

The caloric content of meat per 100g is as follows: boiled chicken 142 kcal, fried chicken 289 kcal, pork loin 204 kcal, pork belly 484 kcal, beef sirloin 357 kcal, beef ribs 312 kcal. During a diet, eating chicken may be better than eating mackerel or sardines.

Nevertheless, the reason fish is considered a health food is due to its fat composition.

Fish contain more unsaturated fats than meat. The DHA (a type of omega-3 fatty acid) content in bluefin tuna reaches 34.6%. Salmon (16.1%) and mackerel (11%) are also rich in DHA. DHA helps maintain vascular health and prevents dry eyes. It is also related to brain cell development and is known to aid in improving memory and learning ability.

When eating fish, be cautious of polychlorinated biphenyls, which are endocrine-disrupting substances.

According to the Ministry of Food and Drug Safety, the average contamination levels of polychlorinated biphenyls from 2012 to 2017 were highest in the following order: seafood, livestock products, processed foods, and agricultural products.

Among seafood, the most frequently detected were ▲whale, ▲gizzard shad, ▲squid, ▲herring, ▲conch, and ▲pollock.

Polychlorinated biphenyls tend to accumulate heavily in fish skins and internal organs, so it is better to remove them before cooking. Boiling is also an option. It is known that boiling and cooking reduce the polychlorinated biphenyl content in food more than grilling.