Our BS meter spikes sky-high when we hear about a new miracle plan that promises fast and easy weight loss. But as this video from TED-Ed explains, fad diets aren't always so obvious. Skip to the two-minute mark for common red flags, including cutting out an entire food group (no carbs!) or limiting yourself to only one type of food (salad all day, every day!). If you're looking for sustained weight loss, developing a customized plan with your primary care doctor or nutritionist is probably your best bet.