As a clinician who works with weight loss and obesity, I can tell you with certainty that people can and do become weight loss resistant and can develop some degree of “metabolic damage”. Metabolic damage is a non-diagnostic term many in the weight loss industry use to describe a set of functional disturbances. These disturbances include severe metabolic compensations that result in a depressed metabolic rate, chronic fatigue, immune suppression, and multiple hormonal effects (i.e. suppressed thyroid function, adrenal stress maladaptation, and loss of libido and/or menses).
^ Jump up to: a b Daskalopoulou, Stella S.; Rabi, Doreen M.; Zarnke, Kelly B.; Dasgupta, Kaberi; Nerenberg, Kara; Cloutier, Lyne; Gelfer, Mark; Lamarre-Cliche, Maxime; Milot, Alain (2015-01-01). "The 2015 Canadian Hypertension Education Program Recommendations for Blood Pressure Measurement, Diagnosis, Assessment of Risk, Prevention, and Treatment of Hypertension". Canadian Journal of Cardiology. 31 (5): 549–68. doi:10.1016/j.cjca.2015.02.016. PMID 25936483.
Hypertension results from a complex interaction of genes and environmental factors. Numerous common genetic variants with small effects on blood pressure have been identified as well as some rare genetic variants with large effects on blood pressure. Also, genome-wide association studies (GWAS) have identified 35 genetic loci related to blood pressure; 12 of these genetic loci influencing blood pressure were newly found. Sentinel SNP for each new genetic locus identified has shown an association with DNA methylation at multiple nearby CpG sites. These sentinel SNP are located within genes related to vascular smooth muscle and renal function. DNA methylation might affect in some way linking common genetic variation to multiple phenotypes even though mechanisms underlying these associations are not understood. Single variant test performed in this study for the 35 sentinel SNP (known and new) showed that genetic variants singly or in aggregate contribute to risk of clinical phenotypes related to high blood pressure.
Recent research indicates prolonged chronic stress can contribute to metabolic syndrome by disrupting the hormonal balance of the hypothalamic-pituitary-adrenal axis (HPA-axis). A dysfunctional HPA-axis causes high cortisol levels to circulate, which results in raising glucose and insulin levels, which in turn cause insulin-mediated effects on adipose tissue, ultimately promoting visceral adiposity, insulin resistance, dyslipidemia and hypertension, with direct effects on the bone, causing "low turnover" osteoporosis. HPA-axis dysfunction may explain the reported risk indication of abdominal obesity to cardiovascular disease (CVD), type 2 diabetes and stroke. Psychosocial stress is also linked to heart disease. http://www.sandysidhumedia.com/wp-content/uploads/2012/12/nailahquote.png
^ Piwernetz K, Home PD, Snorgaard O, Antsiferov M, Staehr-Johansen K, Krans M (May 1993). "Monitoring the targets of the St Vincent Declaration and the implementation of quality management in diabetes care: the DIABCARE initiative. The DIABCARE Monitoring Group of the St Vincent Declaration Steering Committee". Diabetic Medicine. 10 (4): 371–77. doi:10.1111/j.1464-5491.1993.tb00083.x. PMID 8508624.
Between 2006 and 2011, there was a 25% increase in the number of people visiting US emergency rooms for essential hypertension, according to an analysis of data from the Nationwide Emergency Department Sample in 2014.  The reason for the increase, however, remained uncertain. The rate of emergency department visits also increased significantly, according to the study, rising from 190.1 visits per 100,000 population in 2006 to 238.5 visits per 100,000 population in 2011. Over the same period, however, admission rates decreased, from 10.47% in 2006 to 8.85% in 2011. 
How to treat metabolic syndrome is controversial. Because there are several potential markers, the public health community has struggled with the decision of how best to define, diagnose and treat it. Nutritional approaches have generally been downplayed in favor of multiple medications that target the individual markers. Conventional recommendations tend to emphasize caloric restriction and reduced fat intake, even though metabolic syndrome can best be described as carbohydrate intolerance. The most effective treatment for metabolic syndrome is to control the intake of carbs, not fat. In fact, restricting dietary fat and replacing it with carbohydrate actually makes many of the problems of metabolic syndrome worse. The metabolic syndrome paradigm has therefore caused a great deal of distress—and pushback—among those advocating low-fat diets. For more on how to prevent metabolic syndrome, see How to Reduce Your Risk for Metabolic Syndrome.
According to the Mayo Clinic, doctors may use other tests to diagnose diabetes. For example, they may conduct a fasting blood glucose test, which is a blood glucose test done after a night of fasting. While a fasting blood sugar level of less than 100 milligrams per deciliter (mg/dL) is normal, one that is between 100 to 125 mg/dL signals prediabetes, and a reading that reaches 126 mg/dL on two separate occasions means you have diabetes.
[Guideline] Skyler JS, Bergenstal R, Bonow RO, et al. Intensive glycemic control and the prevention of cardiovascular events: implications of the ACCORD, ADVANCE, and VA Diabetes Trials: a position statement of the American Diabetes Association and a Scientific Statement of the American College of Cardiology Foundation and the American Heart Association. J Am Coll Cardiol. 2009 Jan 20. 53(3):298-304. [Medline].
When you have type 2 diabetes, your cells don't get enough glucose, which may cause you to lose weight. Also, if you are urinating more frequently because of uncontrolled diabetes, you may lose more calories and water, resulting in weight loss, says Daniel Einhorn, MD, medical director of the Scripps Whittier Diabetes Institute and clinical professor of medicine at the University of California in San Diego.
The clinical value of using "metabolic syndrome" as a diagnosis has previously been debated due to different sets of conflicting and incomplete diagnostic criteria. These concerns have led the American Diabetes Association and the European Association for the Study of Diabetes to issue a joint statement identifying eight major concerns on the clinical utility of the metabolic syndrome diagnosis. The principal argument has been that when confounding factors such as obesity are accounted for, diagnosis of the metabolic syndrome has a negligible association with the risk of heart disease. http://media-cache-ec5.pinterest.com/upload/21110691974453216_0I4oS4Zs_c.jpg