A diet that provides you with 30 percent less energy than you burn each day works better if you use cod as your source of protein. Researchers from the University of Iceland have published an article on the matter in Nutrition, Metabolism & Cardiovascular Diseases. A low-calorie diet with lean fish works better than an identical diet in which the protein source is lean meat. Fish, protein & weight loss Fish is good for your heart and blood vessels, and for your body composition. Maybe it's because fish contains n-3 fatty acids, maybe it's because fish contains lots of vitamin D, maybe it's because fish protein contains relatively high amounts of the amino acid taurine, which raises the metabolic rate, or maybe it's because of the interaction between all of these factors. It's a fact, people lose weight more quickly if they eat a lot of fish. Animal studies have shown that a low-calorie diet that contains a lot of fish protein maintains the muscles' glucose reserves better than a diet based on other sources of protein. Study The researchers wanted to know what the effect of a high-lean-fish diet would be on overweight men and women. They did a trial with 126 fat people aged between 20 and 40, and put them on a fairly strict diet for 8 weeks. The control group was given lean meat every day, another group was given 150 g cod 3 times a week instead of meat, and the last group ate 150 g of cod 5 times a week. All test subjects got their energy for about 35 percent from fat, 17 percent from proteins and the rest from carbohydrates. Results The figure below shows the changes in the 3 groups after 8 weeks. The more cod the test subjects ate, the greater the effect of their weight-loss diet. The effect of the cod diet was significant for both total weight loss and waist measurement reduction. Eat cod instead of meat five days a week and you'll lose 1.7 kg more in 8 weeks. Sponsors There's just one 'but' about this study: it was paid for by the Icelandic Research Fund AVS. In other words: the Icelandic ministry of fisheries. Fishing is of vital importance to the Icelandic economy: fish accounts for 63 percent of Iceland's exports. You could say the sponsor had a vested interest in the research outcome.
Most of the Oceans are thoroughly polluted though. You'd be taking in a lot of mercury and heavy metals - that's obviously not part of the study. While I like fish as do most people, it's not so rosy due to human activity.
This is mainly true for larger fish as these heavy metals and mercury accumulates. Small fish have a bit of it, but the larger fish eat the smaller fish, leading to more accumulation of these heavy metals. The higher up you go in the marine food chain, the worse it gets.