US researchers found that more people gain weight at the weekend because they tend to binge and party. Do you let your hair down more at the weekends and eat what you like? Studies show that most people tend to lose weight Tuesday but begin to pile it back on Friday because of the lack of discipline when the weekend hits us. Researchers are advising to not worry about what you eat and drink over the weekend, but focus on healthy lunches and dinners during the week.
Do you know what I think however? I think you could lose weight Monday through to Sunday with a healthy balanced diet. You don't need to be mega strict the whole time, a few bad meals here and there won't ruin it for you. Be smart and enjoy your life :)
Reference - Daily Mail - http://www.dailymail.co.uk/health/article-2551562/Want-lose-weight-Try-WEEKDAY-diet-gain-weight-weekends.html