The word “diet” is ambiguous, so I want to clarify that I mean it in the sense of a “nutritional lifestyle”, a pattern of eating that you do your entire life. All research to date tells us that temporary dietary changes can achieve temporary results. What we are really looking for is a new balance with food- to learn and integrate patterns of behavior that you can live with and be happy with. While we want our diet to nourish rather than harm our body, we also know that food serves many purposes beyond nourishment. It is a universal language that that people from any part of the world can relate to and enjoy. It is ritualized into the happiest and darkest moments of our lives. It can be a source of comfort and a reminder of home. When we change our diet, we must respect these other roles that food has in our life or they will fail to achieve the desired result.
There is no consensus on what constitutes the “best” diet for diabetes (or for any medical condition for that matter). This fact is recognized by the American Diabetes Association, as described in their consensus report on nutrition. Everyone agrees that a calorie deficit is needed if you are looking to lose weight, and nearly everyone agrees that diet with a large component of vegetables is important, but outside of these concepts there are differing professional opinions and insubstantial proof of superiority of one diet over another. Ultimately, most diets targeting weight loss will work with similar efficacy as long as you stick to them, leading to the maxim “the best diet is one that you can stick to”1Johnston BC, et al. Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA. 2014..
I say this mostly from a pragmatic perspective. Meals eaten away from home tend to be higher in added sugar and fats, tend to be larger than necessary portions, and tend to be higher in calories. In one study of national restaurant chains in the Phildelphia region, the average adult meal was 1495 calories, 28gm saturated fat (half an appitizer and one entree).
But beyond the common-sense element to home cooking, there is a small but growning evidence base for the benefits of eating home-prepared meals. People who eat home-cooked meals more frequently are more likely to stick to their diet2Mills S, et al. Frequency of eating home cooked meals and potential benefits for diet and health: cross-sectional analysis of a population-based cohort study. Int J Behav Nutr Phys Act., have lower body weight3Mills S, et al. Frequency of eating home cooked meals and potential benefits for diet and health: cross-sectional analysis of a population-based cohort study. Int J Behav Nutr Phys Act., and are less likely to develop diabetes4Zong G, et al. Consumption of Meals Prepared at Home and Risk of Type 2 Diabetes: An Analysis of Two Prospective Cohort Studies. PLoS Med. 2016.
It is an easily demonstrable fact that carbohydrates stimulate a much higher blood glucose rise than an equivalent number of calories from protein or fat. It is also a fact that carbohydrates require more insulin than protein or fat in order to be used by your cells as metabolic fuel.
These figures are data from an experiment on 8 healthy people (4 men, 4 women), each given 4 meals consisting of different macronutrients to evaluate the effect on various blood chemistries. All 8 subjects were given each of the 4 meals, with the following macronutrient components.
Graph 1: Blood glucose changes based off macronutrient content of meal. You can see that the carbohydrate meal stimulated the highest blood glucose rise (7mmol, equivalent to 126mg/dL). Protein had minimal effect on blood glucose levels. Protein with fat had little effect on blood glucose levels. Finally, the mixing of fat with carbohydrate decreased the blood glucose rise stimulated by carbohydrates.
Graph 2: Meal-stimulated insulin level changes based off macronutrient content of meal. You see that carbohydrates stimulate a strong and rapid response to the carbohydrate meal. The addition of additional fat to the carbohydrate meal was associated with a lower insulin spike than carbohydrates alone. The protein and protein with fat meals were associated with far more modest insulin response.
Excerpt from figure 1 from: Collier G, O’Dea K. The effect of coingestion of fat on the glucose, insulin, and gastric inhibitory polypeptide responses to carbohydrate and protein. American Journal of Clinical Nutrition. 1983.
Based off these facts, shifting food consumption from the typical high carbohydrate American diet to one that shifts more of the food intake to fat and protein will result in smaller glucose spikes with meals and lower insulin requirement from the pancreas. While it is not definitively proven that this strategy ultimately results in long-term lower blood sugars and accentuated weight loss, this has been my experience with patients in clinic. There is a lot written about this topic. If you want to go deeper into the argument for low carbohydrate diets in treating diabetes, start here.
The approach I recommend for most of my patients is to restrict carbohydrates to about 30-40% of caloric intake, which still allows people the flexibility to eat real food, but restricts carbohydrates enough to provide the blood glucose control benefit.
For simplicity, my daily carbohydrate cutoff recommendation for most people with diabetes is 100-120 grams per day. This is 30-40% of an ~1300 cal/day diet. Most people will lose weight at that calorie intake, which is the goal for most people with type 2 diabetes, and for many people with type 1 diabetes.
Vegan and vegetarian diets are an excellent option for people with diabetes, since a proper vegetarian or vegan diet can also restrict caloric intake and carbohydrates. These diets will result in lower insulin requirement, reduced glucose fluctuations, improved weight loss, lower insulin resistance, and have the potential to trigger remission of diabetes. I am wholeheartedly in support of this approach to diabetes. I personally have many vegetarian recipes in my diet, and there are over a dozen vegetarian options in the diabetes prescription mealplan. Most of my patients still want to eat meat and/or fish, and this is perfectly fine.
There is a wide range of definitions of “low carbohydrate”, and many of these diets restrict carbohydrates severely. Popular examples include the Keto diet, Atkins diet, and the Bernstein Diabetes Solution. Others popular diets restrict carbohydrates far more modestly, such as the Mediterranean Diet or the South Beach Diet, and these diets may focus on the types of carbohydrates consumed. I have patients that have been on every one of these diets and have had success.
However, I personally can’t live with any of these diets. The extreme low carbohydrate diets are too boring to be maintained long term, and the Mediterranean/South Beach diets are too puritanical from the standpoint of the types of carbohydrates that are recommended.