Research shows that eating the same thing every day may help you lose weight. Psychologists believe that eating the same thing every day results in psychological "habituation" (or boredom), which tends to reduce calorie intake. Also, when you have a plan in place it means you’re less likely to make a fast food run or grab the endless bag of chips.
If you eat the same things day after day you can miss out on important nutrients. Studies have also found health benefits associated with eating a more diverse diet. A 2013 study with over 5200 people found that the greater diversity of healthy foods was associated with a lower risk of metabolic syndrome. A 2002 study published in the International Journal of Epidemiology found that increasing the variety of healthy foods increases life span. Researchers concluded that if you increase the number of healthy foods regularly, you also tend to decrease the number of less healthy foods consumed.
Eating a variety of good foods can play an important role in promoting a greater bacterial diversity in your gut. Bacterial diversity (the “microbiome”) not only may keep the weight in check but also can help prevent more serious illnesses such as diabetes.
What to do? Whatever works best, everything in moderation. Portion controlled servings of many foods is generally recognized to the best choice. Alternatively, you could eat the same thing every day but switch up the menu every week.