If by "periodicity", you mean temporarily switching to a junk food diet before reverting to a balanced diet, your health still suffers during the time that you are on the junk food diet. It would be healthier to restrict calorie intake while sticking with the balanced diet, which would not cause nutritional deficiencies.
Supplements can help make up for some of the deficiencies in a nutrient-poor diet, but no set of supplements will include all of the micronutrients, antioxidants, and other compounds found in a balanced diet of nutrient-dense foods. Most people are better off eating a balanced diet instead of eating junk food and then taking pills to try to fill in some of the gaps.
> Food is a complex mix of vitamins, minerals and phytochemicals (plant chemicals). Phytochemicals are an important component of food and help to reduce the risk of conditions such as heart disease, type 2 diabetes and some cancers. Vitamin and mineral supplements do not provide the benefits of phytochemicals and other components found in food, such as fibre.
> Whole foods usually contain vitamins and minerals in different forms – for example, vitamin E occurs in nature in eight different forms – but supplements contain just one of these forms.
> Vitamin and mineral supplements can’t replace a healthy diet, but a general multivitamin may help if your diet is inadequate or where there is already a well-supported rationale for you to take one. If you feel you could be lacking in certain vitamins and minerals, it is better to look at changing your diet and lifestyle first, rather than reaching for supplements.
Supplements can help make up for some of the deficiencies in a nutrient-poor diet, but no set of supplements will include all of the micronutrients, antioxidants, and other compounds found in a balanced diet of nutrient-dense foods. Most people are better off eating a balanced diet instead of eating junk food and then taking pills to try to fill in some of the gaps.