First, let it be known that I am not a dietician. Only Registered Dieticians and medical doctors have the training and expertise to dispense with diet advice.
That being said, I often get asked by my clients about the best ways to lose weight. In a paper I wrote while studying for a Master's degree in Exercise Science, I detailed some of the challenges in keeping weight loss from returning and the personal strategies I use to lose weight.
I present it here to you now with the caveat that I teach exercise for a living, not nutrition. But this is the sort of general information I give to my clients when they ask about weight loss:
There is confusion among the general public about the best ways to lose weight. While simple on its face (expend more calories than you consume), the fact is that weight loss is unique to each individual and is composed of a dizzying array of hormonal, genetic, and environmental factors.
Standard advice is to eat less and exercise more, and that a 500 calorie a day deficit should lead to a 1lb. per week weight loss. If it were that easy, everyone would be skinny.
The fact is the body seeks homeostasis. When a person starts to lose weight, a host of processes begin in the body to return it to its accustomed weight. For instance, the hormone leptin, which triggers hunger, is increased as the body starts to lose weight. Losing weight might be a "simple" matter of eating less and exercising more, but the body will fight your best efforts to keep that weight loss off as it tries its hardest to get back to homeostasis.
Further, weight loss reduces resting metabolic rates (RMR) in a process called adaptive thermogenesis. Unfortunately, the more one loses, the more RMR is reduced (Evert & Franz, 2017). This effect is measurable even many years past initial weight loss.
So while it is certainly possible to lose 1 to 2 pounds of weight per week, it is not advisable for many individuals. Truly, slow and steady win the race. A more reasonable method, and one I have used successfully myself, is to aim for weight loss in the region of 1 to 2 pounds per month.
This allows the body to slowly reset its baseline homeostasis and helps to prevent the biological drive to regain weight. Weight loss such as this can be achieved by small steps such as eliminating alcohol most of the time or reducing portions. These are goals that can be maintained, as compared with the difficulty of maintaining a low-carb or low-fat diet.
I also try to put on muscle while losing weight to counteract the lowering of RMR. Muscles require more energy to function; therefore, the more lean muscle mass a person has, the more energy she will burn. Unfortunately, weight loss typically reduces lean muscle mass, so measures must be taken to counteract this process.
It should be noted that I am of normal weight and have no chronic conditions. The advice might be different for someone who, for health reasons, needs to lose weight more quickly.
Evert, A.B., & Franz, M.J. (2017). Why weight loss maintenance is difficult. Diabetes Spectrum 30 (3), 153-156.
McGill, E.A., Montel, I.N. (Eds.). (2017). NASM essentials of personal fitness training, 5th Edition. Burlington, MA: Jones and Bartlett Learning.
Zydek, G., Michalcyzk, M., Zajac, A., & Latosik, E. (2014). Low- or high- carbohydrate diet for athletes? Trends in Sport Sciences 4 (21), 211.