Obesity: When Diet Is a Treatment, Not Just a Diet

Charles P. Vega, MD; Caroline M. Apovian, MD


February 06, 2017

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Charles P. Vega MD: Hello. Welcome to this discussion of critical issues in obesity. I am Chuck Vega and I am a clinical professor of family medicine at the University of California at Irvine. I am delighted to be joined by Dr Caroline Apovian. She is a professor of medicine and pediatrics at Boston University School of Medicine. She is also the director of nutrition and weight management at Boston Medical Center. Caroline, great to have you.

Every clinician is familiar with the problem of obesity. According to data from the Centers for Disease Control and Prevention (CDC), more than one third of US adults have obesity.[1] After about a decade of holding pretty steady, obesity increased by 3% among adults between the 2012-2013 period and the 2013-2014 period. The cornerstone of treatment of obesity is lifestyle. I would like to focus on the role of diet in weight loss.

The battle over which diet is best for adults with obesity is intense and enduring. In a meta-analysis published in the Lancet Diabetes and Endocrinology,[2] low-fat diets were associated with a mean of 5 kg weight loss compared with usual diets, which is not too bad. The low-carbohydrate diets were associated with even greater weight loss compared with the low-fat diets. In fact, dietary fat content seemed to have very little impact on weight loss. The concept that dietary fat does not matter in weight loss is shocking to many people.

Let us put this issue of weight loss in a clinical perspective with a case. My next patient is a 50-year-old woman. She has a medical history of type 2 diabetes, hypertension, and hyperlipidemia. She has a body mass index (BMI) of 33 kg/m2 and she says, "I have been heavy as long as I can remember." She has received intermittent diet advice from her healthcare providers, including several visits with a nutritionist. However, she still eats a fairly calorie-intensive, carbohydrate-heavy diet.

Caroline, I am going to kick it over to you. What is the initial approach to this patient with respect to her diet?

Caroline M. Apovian, MD: It could be that the calories that she is taking in are very carbohydrate heavy. She already has diabetes, so she already has insulin resistance. A very quick and easy way to rev up her metabolism, so to speak, is to lower the carbohydrate content in her diet drastically and replace that with protein and some fat—hopefully monounsaturated and unsaturated fats. If you do that, right away insulin levels drop, because less insulin is being stimulated by all of that carbohydrate. Studies have shown that protein and fat are more satiating than carbohydrate, at least simple carbohydrate, and so we probably can get her insulin levels down and get some weight loss by stimulating more satiety with a higher-protein, high-fat diet.

That is probably the first thing I would try to implement. Most people do very well with this approach. The problem is keeping the weight off for the long term, because we live in an environment that is heavily saturated with palatable low-cost foods, and they are mostly very high in sugar and fat. The question is, how long can she stay on a high-protein diet?

What About the Insulin?

Dr Vega: Let me ask a couple of follow-up questions. As she accepts that diet, I assume that there is a discussion, and she gets some advice from a nutritionist about what to do. Will you proactively lower her insulin dose so that she does not run the risk for hypoglycemia, assuming that her carbohydrate load goes way down and therefore her sugars should come under much better control? Do you wait a week? How do you play that out?

Dr Apovian: Yes, you have to reduce insulin dosing because of that lack of carbohydrate. It depends on the patient and anticipated compliance. If you do not lower insulin in the first week, the patient will become hypoglycemic and overeat right away, because that is a very powerful response to hypoglycemia. This diet is not going to work unless you lower the insulin dose. We usually cut it by at least half.

Dr Vega: The other question is about individualizing that therapy. How do you make the transition from this diet to one that includes carbohydrates? How many of these patients can maintain that high-protein, low-carbohydrate diet over time? Is there a period, on average (given that everybody is different), after which you can try to transition into a reasonable amount of carbohydrate and still emphasize that high level of protein?

Dr Apovian: You can take lessons learned from the protein-sparing modified fast. The protein-sparing modified fast is just protein and very little, if any, carbohydrate—a maximum of 20 g daily. In those patients you can essentially cut out the insulin and sulfonylurea, if your patient is diabetic, and replace these drugs that cause weight gain. Those drugs create a vicious cycle, and you are basically making the diabetes worse in the end.

We now have GLP-1 agonists, SGLT-2 inhibitors, and metformin. These drugs help the patient lose weight and improve insulin sensitivity. You can switch patients on insulin and sulfonylurea to these drugs and have them follow a high-protein diet in which very little calories come from carbohydrate. You do not want to continue that for more than 12-16 weeks. After that you can start slowly introducing carbohydrate with vegetables and then eventually whole grains and fresh fruit. You watch the patient's blood sugar; they should be stabilized on much lower doses of diabetes medications. If you have a patient in whom you intervened quickly enough into their diabetes history, you may be able to keep them off of insulin and sulfonylureas.

Dr Vega: Avoiding that vicious cycle is wonderful. My final question is about the clinical applicability of diets that are more intensive, which include drastically limiting carbohydrate, fasting, or following a liquid diet. How are these diets accepted among the general patient population with obesity? Have you found in counselling patients that you can get them to buy into and commit to these diets in a meaningful way?

Dr Apovian: The first thing to let them know is that this is not a diet. This is a treatment for your diabetes.

Dr Vega: Good point.

Dr Apovian: That is especially the case when you are talking about the protein-sparing modified fast. That was never a diet. It was always treatment for obesity, uncontrolled diabetes, and uncontrolled metabolic derangements, and it was originally studied in the hospital setting. If you look at the early papers written by George Blackburn and Bruce Bistrian,[3,4] they were giving intravenous amino acids to obese patients in the inpatient unit and they found that you could spare muscle mass. That is why it is called protein-sparing; the patient loses fat and increases fat mobilization.

The protein-sparing modified a treatment. It is like a drug.

It is a treatment. It is like a drug. You need to let the patient know, "You are not on a diet here; this is a treatment, and we have to carefully monitor you," especially patients with diabetes. There should be visits every week with the physician who is prescribing this treatment. If patients cannot come in every week, at least have phone calls. Blood work has to be done periodically with a protein-sparing modified fast to make sure that the patient does not have hypokalemia, hypomagnesemia, or hypophosphatemia. If that develops, those [minerals] need to be replaced. We always give patients extra potassium when they are on this treatment.

Dr Vega: Excellent point. This diet is something that we certainly should encourage other physicians to use as a tool—as a treatment, not as a diet. That is a great selling sales point. It really can make a difference for patients, particularly in the shorter term to give them the motivation and the hope that they can do this over time as well. That is where they will reap the benefits—over years.

Caroline, thank you so much for the great answers, as always. We are going to talk to you once more about the option of bariatric procedures. Stay tuned for that, everybody. Thank you for tuning in.

Follow Dr Apovian on Twitter at @DrApovian


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