Type 2 diabetes mellitus (T2DM) is a highly lifestyle-dependent metabolic disease. Its global prevalence is predicted to reach 300 million by 2025, increasing concomitant with obesity and the global adoption of a sedentary lifestyle. This has worrying public health and economic implications (Hussain, Claussen, Ramachandran, & Williams, 2007).
Atkins’ Nutritional Approach (ANA) is a low-carbohydrate ketogenic diet (LCKD) for weight loss. Protein and fat make up most of the calories in ANA (Atkins, 2002) (see Appendix A).
This report describes T2DM, its conventional treatment, and discusses treatment using ANA. The author describes his experiences of ANA, and records progress statistics (body mass index (BMI) and waist circumference; see supporting document). The document concludes with statements of reflection on the diet and on the author’s learning experience.
T2DM is characterised by hyperglycaemia, as diagnosed by elevated fasting plasma glucose (FPG) and oral glucose tolerance testing (OGTT). Glycosylated haemoglobin (HbA1C) tests are also used (American Diabetes Association, 2011).
Symptoms of hyperglycaemia include polyuria, thirst, blurred vision, weight loss, dry skin and fatigue. If untreated, symptoms include ketoacidosis, coma and death (World Health Organisation, 1998).
T2DM complications produce major signs and symptoms (Figure 1).
Hyperglycaemia is associated with insulin resistance, where body tissues produce a weaker-than-normal response to a given amount of insulin. This is accelerated by increased adiposity, causing increased insulin secretion from pancreatic beta cells, and poor glycaemic control. Long term, this can cause beta cell exhaustion, and relative insulin deficiency compared to demand (Kumar, Abbas, Fausto, & Aster, 2010).
A primary risk factor for T2DM is obesity (BMI >30; vide supra). Genetic factors and family history also contribute, but the current epidemic is mostly caused by excessive energy intake versus expenditure (Sladek et al., 2007).
Other risk factors include age, hypertension, low HDL and high triglyceride concentrations, and polycystic ovarian syndrome or gestational diabetes (National Centre for Biotechnology Information, 2011).
T2DM contributes up to 95% of all diabetes mellitus (DM) cases. Between 2000 and 2010 the Australian DM prevalence increased 33% (1.0 to 1.3 million) (Zimmet, Alberti, & Shaw, 2001).
Aboriginal and Torres Strait Islander, Polynesian, Micronesian, Indian and Chinese are at increased risk. In developed countries, T2DM is more common in lower socioeconomic groups. Education is implicated in this discrepancy. The reverse is true for developing countries (Shaw & Chisholm, 2003).
Hyperglycaemia causes T2DM complications, including nephropathy/renal failure, neuropathy, foot ulcers, neuropathic arthropathy, retinopathy, blindness and hypertension (Figure 1) (National Centre for Biotechnology Information, 2011). Cardiovascular disease (CVD) and stroke incidences are also increased (World Health Organisation, 1998).
Complications are common in unmanaged diabetics. The mortality rate of DM patients is three times that of other Australians, and T2DM is a leading cause of death in Australia (Australian Institute of Health and Welfare, 2009; Australian Bureau of Statistics, 2006). Diabetics have poor quality of life (Figure 2).
Diet and exercise are important T2DM treatments, reducing incidence, complications and mortality (Pate et al., 1995).
Pharmaceuticals are available (e.g. metformin, ascarbose and exogenous insulin) and most effective when combined with lifestyle changes (American Diabetes Association, 2010).
Care also involves counselling and teaching the patient to monitor blood glucose, administer insulin, and maintain healthy weight (Figure 3).
Figure 3: Management of T2DM (Ripsin, Kang, & Urban, 2009)
The principle of ANA (see Appendix A) is that limiting dietary carbohydrates induces ketosis, similar to prolonged starvation (Figure 4).
Limited dietary carbohydrate lowers blood glucose, stimulating glucagon and suppressing insulin secretion. This activates glycogenolysis in liver and skeletal muscle, maintaining blood glucose until glycogen stores deplete. Suppressed insulin secretion inhibits triacylglycerol (fat) deposition and stimulates lipolysis. Since animals cannot synthesise glucose from fatty acids, ketone bodies become the primary blood “transport molecule” for acetyl groups from lipolysis. This state is called ketosis. Gluconeogenesis synthesises glucose from glycerol/lactate/amino acids in the liver. This glucose complements ketones in fuelling tissues (e.g. brain) that cannot oxidise fat, and maintains blood glucose upon glycogen depletion. Erythrocytes depend completely upon glucose (Westman, Mavropoulos, Yancy, & Volek, 2003).
Insulin and blood glucose “spikes” are associated with high-carbohydrate meals, not high-fat/protein meals, so LCKDs may improve glycaemic control (Hall, 2011). In hyperglycaemia, glucose reacts with endogenous proteins, impairing their function. This glycosylation is implicated in the pathogenesis of T2DM complications, and may be reduced by lowered blood glucose in LCKDs (Kumar et al., 2010).
Ketosis involves lipolysis for energy production, and gluconeogenesis, an inefficient endothermic process, to maintain blood glucose (Hall, 2011). These processes accelerate weight loss, important in T2DM treatment. The inefficiency of gluconeogenesis can allow weight loss despite excess caloric intake. Patients don’t feel “constantly hungry” since calories aren’t restricted. Unlike starvation, loss of muscle tissue is avoided by dietary protein and fat intake. Ketones suppress appetite, so ANA also improves satiety (Westman et al., 2003).
Weight loss improves the prognoses of T2DM patients, mainly through reducing insulin resistance, but which diet to recommend is controversial (Davis, Forbes, & Wylie-Rosett, 2009).
Conventional low glycaemic index dietary treatments for T2DM comprise whole grains, fruit and vegetables, complemented with omega-3 fatty acids and unsaturated fats (Hu & Willett, 2002; Mann, 2002).
ANA involves unrestricted fat and protein intake, and small amounts of vegetables, fruits and whole grains once healthy weight is achieved (see Figures 4 & 5) (Atkins, 2002).
Figure 6: A "food pyramid" summarising scientifically accepted nutritional guidelines (Harvard University School of Public Health, 2011)
American Diabetes Association (2007) does not recommend LCKDs in T2DM management. However, LCKDs are effective in weight loss and glycaemic control, increasing insulin sensitivity and improving lipid profiles (HDL/LDL ratios increased, decreased total cholesterol and triglyceride) for up to two years (Shai et al., 2008; A. J. Nordmann et al., 2006). Yancy, Foy, Chalecki, Vernon, & Westman (2005) showed that a 16-week LCKD significantly decreased glycosylated haemoglobin and fasting blood glucose in T2DM patients (Figures 6 & 7).
Limited studies exist on long-term safety of ANA. Ketogenic diets used to treat epilepsy reveal increased kidney disease rates (Kossoff et al., 2002). Brenner, Meyer, & Hostetter (1982) implicated increased protein intake in nephropathy. However, ANA may alleviate some nephropathy by treating T2DM.
High fat and protein intake may cause CVD (particularly atherosclerosis) long-term (Kavey et al., 2003). One systematic review of LCKDs revealed no increase in CVD risk factors (HDL/LDL) over one year (Dena M. Bravata et al., 2003). Other studies showed improvement (Shai et al., 2008; A. J. Nordmann et al., 2006). In contrast, overweight/obesity and CVD risk correlate strongly (Figure 8). Longer-term studies are required.
Figure 9: Population attributable risk percentage effects for overweight and obesity on CVD risk factors and events in Framingham men and women followed up for 44 years (Wilson, D’Agostino, Sullivan, Parise, & Kannel, 2002)
Despite unknown harms, physicians and patients may try ANA because of rapid (and motivating) weight loss with increased satiety and unrestricted caloric intake, and optimistic short-term trials.
Caution should be exercised. Previous diabetes treatments (e.g. Avandia) were associated with increased risk of CVD events once on the market, although, like ANA, short-term trials were optimistic (Wooltorton, 2002). LCKDs can lower blood glucose, so patients require supervision to prevent hypoglycaemia (Westman, et al., 2003).
ANA is a controversial dietary therapy that may be used to effectively treat T2DM and its complications. However, its potential risks do not warrant its use over current conservative therapies.
Lifestyle interventions for T2DM require ongoing care and support. The dieting process is physically and emotionally draining, and information/support services would likely improve patient outcomes.
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Below is a summary of the phases of ANA, as described in Atkins (2002). Note: 1) that the author’s diet was that described in “Phase 1”, since this represents the beginning of the programme and 2) that Atkins (2002) encourages regular exercise and vitamin/mineral supplements to complement the ANA
Phase 1 (“Induction”; at least two weeks – length depends on personal preference):
- Less than 20g of daily carbohydrate, chosen from vegetables and green salad (e.g. lettuce, small amounts of broccoli; Atkins (2002) provides a list of allowed vegetables).
- Liberal fat and protein intake (e.g. fish, red meat, chicken, eggs). Cheeses are also allowed.
- Recommended drink is water. Caffeine should be avoided but is allowed.
- Alcoholic beverages are prohibited.
- Some artificial sweeteners are allowed: sucralose is preferred.
- Avocadoes, olives, sour cream and full cream (unsweetened) are allowed in moderation, though may curtail weight loss
Phase 2 (“Ongoing Weight Loss”; begins once approaching a comfortable weight – designed to slow weight loss to allow more food options):
- Add 5g of daily carbohydrate per week until no longer losing weight. The daily carbohydrate intake at this point is the “Critical Carbohydrate Level for Losing” (CCLL)
- A list (“The Carbohydrate Ladder”) of carbohydrate-containing foods in the order in which Dr Atkins advises they be introduced into the diet is provided in Atkins (2002). The list is in order of increasing carbohydrate content
Phase 3 (“Pre-Maintenance”; begins once within 5-10 pounds (~0.5-1.0 kg) of desired weight):
- Add 10g of daily carbohydrate per week until weight gain begins, then cut back 10g. This is the “Critical Carbohydrate Level for Maintenance” (CCLM)
- Any added food that promotes weight gain/cravings should be avoided
Phase 4 (“Life Maintenance”; begins once desired weight is reached and CCLM is achieved):
- Continue eating at the CCLM, but try a variety of foods (in moderation) from the allowed list in Atkins (2002). (Sugar is never allowed).
- If weekly weigh-ins reveal that weight is more than 5 pounds (~0.5 kg) above the desired weight, Phase 1 is re-entered, followed by return to Phase 4 once desired weight is returned.