There aren't specific foods that make you fat. Too much of any food can lead to weight gain. The ones that make you fat most quickly are, predictably, those with lots of sugar, fats and refined grains. These foods provide easily digested and processed calories with minimal nutrition content.
In an effort to identify the lifestyle habits most likely to cause weight gain, Harvard University researchers reviewed the habits and diets of more than 100,000 non-obese people to determine the choices that cause weight gain over time. The study, which was published in a June 2011 issue of The New England Journal of Medicine, found that a handful of foods were tightly linked to weight gain.
Read more: The Ultimate Guide to Fat Loss
Avoid Refined Starchy Foods
Potatoes, especially the processed versions, such as potato chips, french fries, hash browns and mashed varieties, are among the most likely foods to contribute to weight gain, especially when eaten in excess.
Other refined starches, such as white bread, pasta and crackers, are also among the foods that will easily pack on pounds. These foods have little fiber to slow digestion, so they convert to glucose almost immediately and spike your blood sugar, which raises your insulin levels.
Insulin allows for the quick delivery of glucose to your fat cells. If you keep your insulin levels high by eating an abundance of starches, the insulin makes it hard for the fat cells to release that energy for fuel. You keep storing fat, but never efficiently burn it.
Cut the Sugar
Desserts and sugary treats — candy, ice cream, pastries, muffins, cakes and cookies — also correlate with fast weight gain, as demonstrated the Harvard study. They have the same effect on blood sugar and insulin as starches.
Sugary sweetened drinks are another product associated with dramatic weight gain. According to the Center for Science in the Public Interest, people who drink one or more sugary drinks per day have a 27 percent higher chance of becoming obese. In addition, the CSPI reports that consuming a sugary drink every day for six months increased fat deposits in the liver by 150 percent.
Eat Less Red Meat
Red meat, as well as processed meat such as hot dogs and sausage, also correlates with weight gain, showed the Harvard research. An earlier study published in an August 2010 issue of the American Journal of Clinical Nutrition showed red meat consumption correlated with weight gain in overweight and normal weight subjects over a five-year span.
Red meat and processed meat often contain large amounts of saturated fat, too much of which can pose a health risk in terms of heart disease, cholesterol levels and high blood pressure. A July 2014 study published in Diabetes showed that participants who overate saturated fat gained notable belly fat in seven weeks, compared to participants who overate polyunsaturated fats. Those who consumed the healthy fats found in nuts, olive oil and avocado gained similar weight, but more in the form of lean muscle tissue.
Watch Those Ultra-processed Foods
Excessive consumption of ultra-processed foods can contribute to weight gain. These foods contain additives — which can be carcinogenic — and high levels of sugar, salt and fat.
Consuming ultra-processed foods can lead to increased calorie. A July 2019 study published by Cell Metabolism, examined the effects of a diet high in ultra-processed foods and a diet of unprocessed foods on overall daily caloric intake. This small study of 20 participants showed that on average, people on the ultra-processed diet ate 500 more calories per day compared with the unprocessed diet. The study concluded that a diet high in ultra-processed foods leads to increased calorie intake and weight gain, But more research with a larger sample size is necessary before formal claims can be made.
Read more: The 7 Principles of Fat Loss
Foods That Discourage Fat Gain
If you're trying to keep weight gain at bay, eat more vegetables, nuts, fruits and whole grains. These foods were less likely to cause weight gain according to the Harvard study. Dairy also did not lead to fat accumulation.
Moderating portions also keeps your body at a healthy weight. Enjoy a treat now and then, but nightly desserts, soda and processed snacks are a recipe for an unhealthy body. Choose low-calorie, nutrient-rich options to satisfy the munchies but keep from packing on fat. Air-popped popcorn, fresh fruit and low-fat yogurt are options.
- The New England Journal of Medicine: "Changes in Diet and Lifestyle and Long-Term Weight Gain in Women and Men"
- Journal of Clinical Investigation: "Consuming Fructose-Sweetened, Not Glucose-Sweetened, Beverages Increases Visceral Adiposity and Lipids and Decreases Insulin Sensitivity in Overweight/Obese Humans"
- American Journal of Clinical Nutrition: "Meat Consumption and Prospective Weight Change in Participants of the EPIC-PANACEA Study"
- Diabetes: Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans
- Cell Metabolism: "Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake"
- Center for Science in the Public Interest: "Facts on Health Risks of Sugar Drinks"