Have you experienced a steady increase in weight gain but haven’t been eating more or find losing weight to be resistant despite reducing calories and increasing activity?
Most people commonly attribute weight gain and being overweight to overconsumption relative to energy expenditure (physical activity), often referred to as the energy balance model (EBM). However, evidence does not entirely support this simplistic assumption. According to national data, since 1980 obesity prevalence in the US has soared from 14% to over 42% however total calories consumed by the average American adult has not risen at a level consistent with this increasing weight trend.
Another model that researchers discuss as an alternate driving force in the obesity epidemic is the carbohydrate-insulin model (CIM). Rather than attributing overeating as the cause of weight gain, the CIM is focused on the modern dietary patterns characterized by excessive intake of high glycemic foods; in particular processed, rapidly digestible carbohydrates. (A food’s glycemic index and glycemic load indicate how quickly and how much it will increase your blood glucose levels.)
Is a calorie a calorie?
According to the CIM, the source of a calorie plays a significant role in weight gain and metabolism. When we eat highly processed carbohydrates such as white rice, white bread, cookies/cakes, chips, etc. a rise in blood glucose triggers the release of insulin. Insulin signals fat cells to rapidly take up this influx of glucose released into your bloodstream. As a result of the rapid uptake our blood sugar level drops. The brain perceiving that the body needs energy induces cravings and feelings of hunger as well as slows our metabolism to conserve energy. Unlike foods high in fiber which are more slowly digested and create a sense of fullness and support stabilizing blood glucose levels.
Additionally, as processed carbohydrates are rapidly and completely digested in the stomach and small intestine this results in insufficient nourishment for our gut microbiome which predominantly resides in our large intestine. A dietary pattern of eating high glycemic foods will have an impact on our healthy gut microbiome composition.
What are obesogens and can they be contributing to weight gain and weight loss resistance?
Multiple environmental factors can also affect obesity susceptibility including stress, sleep/disrupted circadian rhythm and environmental chemicals known as obesogens (a sub-set of endocrine disrupting chemicals).
Our body doesn’t know what to do with the extensive toxins we are exposed to daily. Many of these toxins can disrupt liver function as it works to detoxify this burden on our bodies. Additionally, these obesogens contribute to weight gain through various mechanisms including increasing the number of fat cells, increasing the size of fat cells or disrupting signaling pathways affecting factors such as metabolism and appetite.
As most of these toxins are stored in fat cells, our brain which is two-thirds fat is extremely vulnerable to the effects of these toxins.
Where are these obesogens found in our day-to-day lives?
Unfortunately, obesogens are pervasive in our environment today. To date about 50 chemicals have been identified as obesogens. See table below; source EWG.org
| Chemical | Product |
| BPA, BPS | Food packaging, thermal paper (receipts), food and storage containers, especially cans |
| Persistent organic pollutants; dioxin and PCBs | Air pollution, food, especially animal products |
| Flame retardants | Upholstered furniture, dust, carpet and carpet padding, vehicles, baby clothing, baby products like nap mats, kitchen appliances, bed linens and electronics |
| Food additives; fructose, high-fructose corn syrup, artificial sweeteners; emulsifiers, BHA, MSG | Processed foods and drinks, soda |
| Heavy metals (arsenic, cadmium, lead) | Food and baby food, cosmetics and personal care products, drinking water |
| Parabens | Preservatives in food, paper products, personal care products and pharmaceutical products |
| Pesticides; DDT/DDE, glyphosate, chlorpyrifos,* imidacloprid, permethrin, atrazine, triflumizole | Conventional fruits and vegetables, animal products (DDT/DDE), drinking water (atrazine) |
| PFAS | Food and storage containers, cookware, stain- and water-repellant clothing and other consumer products, dust, water food packaging and wrappers, drinking water, toys, personal care products, medical supplies |
| Phthalates | Plasticizing agent found in food packaging, cosmetics, paint, dust, medicine, flooring materials and wall coverings, and lacquers, varnishes and coatings |
| Organotins such as butyltin, dibutyltin, tributyltin | PVC stabilizers, antifungal paint used on ships (potential seafood contamination) |
| Polycyclic aromatic hydrocarbons, or PAHs | Burning coal, oil, gas, wood, garbage and tobacco, motor vehicle exhaust, gasoline additive, grilled or charred meat or food |
* Banned from use on food in 2021 but allowed for non-food uses.
What can you do for yourself to support a healthy weight?
- Stay active.
- Eat whole or unprocessed foods; eating a varied, colorful and nutrient dense diet. Focus on fresh and frozen foods high in fiber.
- Avoid highly processed foods (high glycemic) which often contain high fructose corn syrup, preservatives and artificial sweeteners, flavorings and colorings.
- Minimize exposure to food packaging (plastic, cans). Preparing whole food meals at home helps reduce exposure.
- As possible eat organic to minimize exposure to pesticide residues. Use EWG’s “Dirty Dozen” and “Clean 15” lists as guidance.
- Consult the Seafood Watch Consumer Guides by the Monterey Bay Aquarium for guidance on seafood choices
- Choose unscented products to minimize exposure to chemicals in fragrances.
- Use a high-quality water filter. Drink water often throughout the day
- Use glass, stainless steel or porcelain storage containers for food.
- Avoid non-stick cookware
- Avoid microwaving foods and beverages in plastic containers
- As possible use “clean” household chemicals and yard/gardening products
Sources:
Heindel JJ, Lustig RH, Howard S, Corkey BE. Obesogens: a unifying theory for the global rise in obesity. Int J Obes (Lond). Published online January 11, 2024. doi:10.1038/s41366-024-01460-3
Mozaffarian D. Perspective: Obesity-an unexplained epidemic. Am J Clin Nutr. 2022;115(6):1445-1450. doi:10.1093/ajcn/nqac075
Holtcamp, W. (2012). Obesogens: An Environmental Link to Obesity. Environ Health perspect. 120(2): a62-a68.doi: 1289/ehp.120-a62
EWG. Are food and consumer product chemicals contributing to our obesity crisis?. Are food and consumer product chemicals contributing to our obesity crisis? | Environmental Working Group (ewg.org). Accessed February 24, 2024
Metagenics Institute. Obesity & Environment: Obesogens, Hormones, and Weight. Obesity & Environment: Obesogens | Metagenics Institute. Accessed February 24, 2024.
