Eating too much junk food can have a negative effect on your general health and wellbeing and can also reduce your ability to be active. Short-term effects of junk foods As well as causing you to gain weight, the other short-term effects of eating junk food include: increased stress levels fatigue and decreased energy levels difficulty sleeping concentration difficulties feeling down tooth decay Long-term effects of junk foods In the long-term, eating junk food can lead to: type 2 diabetes heart-related problems (such as cardiovascular disease, high blood pressure and cholesterol) overweight and obesity osteoporosis certain cancers depression eating disorders These complications are all associated with a diet high in sugar, salt, trans- and saturated fats and with a lack of essential nutrients like fibre, vitamins and minerals.