Weight Management in Patients with Type 1 Diabetes and Obesity

Insulin is anabolic hormone that plays a role in inhibiting protein catabolism, stimulating lipogenesis, and slowing basal metabolism [4, 5, 9], resulting in increased fat accumulation [9, 10]. Inhibiting protein catabolism is another anabolic process, in which weight gain may also occur through an increase in lean body mass [11]. These effects are enhanced by exogenous insulin administration [4], since exogenous insulin imperfectly mimics endogenous secretion [9, 12]. While endogenous insulin has its first pass to the liver through the portal vein to suppress gluconeogenesis [9], exogenous insulin circulates systemically first and disproportionately affects muscle and adipose in comparison to the liver [9].

Double diabetes is a new term used to describe patients with T1D who also show clinical signs of type 2 diabetes (T2D) such as obesity and insulin resistance (IR) [12, 16••]. With the rising rates of overweight and obesity among patients with T1D, there are no longer clear divisions between the two major diabetes subtypes except at time of diagnosis, as the disease appears to behave as a continuum with the two components of its etiology, insulin deficiency, and IR [12]. Double diabetes tends to occur when the pro-inflammatory state associated with metabolic syndrome leads to reduced glycemic control, eventually requiring higher daily doses of insulin [18•]. Increasing insulin dosage due to IR can lead to further weight gain, thus exacerbating the weight problem [18•]. Patients with T1D who are overweight or obese are at a greater risk of developing double diabetes due to their significantly elevated levels of osteopontin (OPN) [19]. OPN is a sialoprotein associated with normal physiological processes as well as autoimmune disease and has been demonstrated to induce adipose tissue inflammation, increase pro-inflammatory cytokine release, and promote development of IR [20]. Fortunately, weight loss reduces circulating OPN concentrations [19]. Double diabetes is a cyclical mechanism of weight gain and IR that should be recognized and treated early.

Increased physical activity to enhance weight loss is widely accepted, but adults with T1D tend to partake in less physical activity than adults without diabetes [21]. The main barrier to physical activity reported is fear of severe hypoglycemia [21]. Though this is a clear psychological barrier, it is also a valid concern since hypoglycemia is the most common adverse event of physical activity in patients with T1D [22]. Hypoglycemia may occur during or up to 24 h after activity [22]. To prevent hypoglycemia, patients usually reduce their insulin dose before exercise, but this strategy can only be used when exercise is planned in advance [23]. An additional drawback is that patients try to keep their blood glucose higher before exercise in order to maintain proper glycemic profile during and after exercise [23]. They do that by increasing consumption of carbohydrates before and during exercise, which results in increased energy intake and consequent weight gain [23].

The American Diabetes Association recommends weight loss for all overweight or obese individuals with diabetes or at risk for diabetes [24]. Many nutrition-based approaches for weight loss have been studied in individuals with or without diabetes, but very few studies were specific to patients with T1D. For patients with T2D, certain macronutrient compositions such as low-carbohydrate or low-fat calorie-restricted diets and different eating patterns including Mediterranean and vegetarian dietary plans were shown to be successful for up to 2 years [24]. In a 2-year study comparing low-carbohydrate, low-fat, and Mediterranean dietary plans in obese participants, mean weight loss was 2.9 kg in the low-fat group, 4.4 kg in the Mediterranean diet group, and 4.7 kg in the low-carbohydrate group [25]. Among the 36 participants with T2D in the study, the Mediterranean diet, which is rich in vegetables and healthy fats and low in red meat, was the most favorable for changes in fasting plasma glucose and insulin levels [25]. The low-carbohydrate diet resulted in the greatest HbA1c reduction of 0.9% over 2 years [25]. Plant-based vegetarian or vegan diets [26] and the Dietary Approaches to Stop Hypertension (DASH) diet [27] have also been shown to induce weight loss and modest improvements in diabetes management. The low-fat vegan diet, devoid of all animal products, was associated not only with sustained weight reduction but also with reductions in total cholesterol and LDL-cholesterol in comparison to a cohort following the American Diabetes Association guidelines [26]. In a similar study, participants on a vegan diet had a decrease in HbA1c, attributed to loss of visceral fat [28]. Less restrictive vegetarian diets also promoted weight loss and reduced HbA1c [29]. The DASH diet, emphasizing vegetables, fruit, low-fat dairy, nuts, seeds, and whole grains while limiting meat, poultry, eggs, and oils, has shown beneficial effects on body weight, total and LDL-cholesterol, and insulin sensitivity [30].

Although these dietary plans, with different macronutrient compositions, have been shown to induce significant weight loss, the American Diabetes Association has determined in its position statement that there is no ideal macronutrient composition for meal plans. Current recommendations state that patients with diabetes should work with nutritionists to develop individualized eating plans based on the patient’s metabolic status, life circumstances, and food preferences [24].

Regardless of macronutrient breakdown, total energy intake must be appropriate to the weight management goal [24]. However, there are distinctions to be made in the quality of macronutrients and how they affect CVD risk factors and glycemic parameters [31•]. For carbohydrate consumption, intake of dietary fiber has been inversely associated with all-cause mortality in diabetes, while high glycemic load and sugar intake were associated with increased mortality [32]. In patients with T1D, meals with the same carbohydrate content but different glycemic indices produced significant differences in postprandial blood glucose, with low GI meals producing a 20% lower glycemic response than high GI meals [33]. For protein consumption, diets containing leaner sources of protein such as chicken and soy result in more favorable lipid profiles than diets containing red meat [34]. For fat consumption, type and source of fat are more important than the percentage or total amount of fat [35]. Diets containing foods high in monounsaturated fatty acids, such as extra-virgin olive oil and nuts, decreased CVD risk [36] and should therefore replace saturated and trans fatty acids [35].

Although weight loss can be achieved with only restriction of energy intake, increasing physical activity and incorporating exercise training into a weight loss plan lead to greater loss of fat mass and preservation of lean muscle mass compared to energy restriction alone [37, 38]. Additionally, there are metabolic benefits to partaking in physical activity for weight loss [37]. In patients with T1D, physical activity has been shown to decrease cardiovascular risk and mortality [39], in addition to improving lipid profile and endothelial function [40]. In patients with T2D, physical activity improves insulin sensitivity [39, 41]. As explained earlier, IR is not unique to those with T2D, as patients with T1D tend to be more insulin resistant than their counterparts without diabetes [39]. Therefore, the benefits of exercise on insulin sensitivity are pertinent to this population, especially in those who are overweight or obese.

Highly variable data exists as to what type of physical activity is best suited for weight reduction. Resistance training alone is associated with fat loss but has minimal effect on overall weight loss [42]. Even when resistance therapy is combined with aerobic training, this seems to lead to a similar amount of weight loss as aerobic training alone [37, 42]. One study showed that aerobic exercise was shown to lower visceral adipose tissue to a greater extent than progressive resistance training when compared to control groups [43]. However, the major benefit of resistance exercise is to preserve lean muscle mass during weight loss [44]. This is especially important since patients with diabetes have progressive lean muscle loss as they age [45].

In terms of exercise intensity, some studies have shown that high intensity interval training (HIIT), consisting of repeated bursts of rigorous exercise immediately followed by low intensity recovery, can lead to significant reductions in abdominal fat [46‐48]. However, other evidence showed that while this approach is time efficient, it is no more effective than continuous moderate aerobic exercise in promoting fat loss [49]. This supports the observation that rigorous and moderate intensity aerobic training results in similar amounts of weight loss when intensities of physical activity are matched in energy expenditure [42]. Patients can partake in the type of physical activity they find most suitable as long as their energy expenditure is in line with their weight loss goals. Risk of hypoglycemia during or after exercise can be minimized if blood glucose is closely monitored before, during, and after exercise, and individual adjustments in insulin or food intake are made [50]. Patients with T1D should be safely able to participate in aerobic or weight-based physical activities if appropriate pre-exercise measures are taken [51••].

This procedure reduces stomach size by creating a small 15–30-mL gastric pouch [94]. While the mechanisms by which it improves blood glucose are only partially understood, there is good understanding of how it enables weight loss [94]. This surgery alters different gut hormone responses including GLP-1 and ghrelin, a potent hunger hormone [94]. After gastric bypass operations, GLP-1 secretion in response is significantly increased and this is presumed to contribute to the observed improvement in glycemic control [95‐98]. It has been suggested that this surgery does not have a similar benefit on glycemic control if residual beta cell function is absent [99, 100].

A study comparing different types of bariatric surgeries found that complications are more likely to occur with RYGB than with sleeve gastrectomy [101]. Another study suggests that many patients who initially have remission from T2D relapse at some point after these procedures, particularly with RYGB and biliopancreatic diversion [87]. There is also a recognized risk of postprandial hypoglycemia [102] and weight regain after this procedure [103].