--- title: "10 Foods That Cause Weight Gain (and What to Eat Instead)" url: https://realfoods.app/foods-that-cause-weight-gain description: "Sugary drinks, potato chips and ultra-processed snacks are linked to weight gain. See 10 everyday foods, from yogurt to granola, and the swaps that help." last_modified: 2026-10-06T08:00:00Z --- 5 min read · Updated October 6, 2026 # 10 Foods That Cause Weight Gain (and What to Eat Instead) By [Dino Pohilj](https://realfoods.app/authors/dino-pohilj), Founder, RealFoods · Drafted with AI > Quick answer > > Refined carbohydrates, sugary drinks and ultra-processed snacks are among the foods most strongly linked to weight gain, because they tend to raise blood sugar and insulin quickly and are easy to eat in large amounts. > > In a [NEJM study of 120,877 U.S. adults](https://pubmed.ncbi.nlm.nih.gov/21696306/) (Mozaffarian et al., 2011), potato chips, potatoes and sugar-sweetened drinks showed the strongest links to weight gain, and in an [NIH inpatient trial of 20 adults](https://pubmed.ncbi.nlm.nih.gov/31105044/) (Hall et al., Cell Metabolism, 2019) ultra-processed meals led people to eat substantially more and gain about 0.9 kg in two weeks. The ten foods below score 6 to 9 on the 1 to 10 Weight Impact Score (the Fat-Burning Paused and Keeping Fat zones) because many are sold as healthy yet raise insulin: sports drinks lead at 9/10, with flavoured low-fat yogurt, granola and protein bars at 8/10. A swap, not a ban, is the place to start. Not all weight gain comes from obvious culprits like fast food and chocolate. In the insulin index study, equal-calorie portions of common foods produced very different insulin responses, and bakery products raised insulin more than their blood sugar response predicted ([Holt et al., 1997](https://pubmed.ncbi.nlm.nih.gov/9356547/)). We argue that some of the biggest obstacles to weight loss sit in the "healthy eating" aisle of the supermarket. These are foods that tend to raise estimated blood sugar and insulin, which may be one reason the scale does not move even when effort is high. Each entry below shows the Weight Impact Score at a standard 100g serving. 📏 How to read these scores The scores below are RealFoods' modelled estimates of each food's blood sugar and insulin impact at a **standard 100g serving**. In the RealFoods app, your actual WI Score adjusts dynamically based on your logged portion size, eating 300g of white rice instead of 100g will push the score higher for starchy, high-scoring foods. Low-scoring foods like chicken or eggs stay low regardless of portion. ## 1. Is flavoured low-fat yogurt bad for weight loss? 8/10 • Keeping Fat Often, yes, because the added sugar makes it a fast sugar hit. When manufacturers take the fat out of yogurt, it tastes like chalk. To make it palatable, they add massive amounts of sugar or fruit purees. While it might be low in calories, it can trigger a sharp blood sugar spike, which is why it scores high. ## 2. Is fruit juice bad for blood sugar, even fresh-pressed? 7/10 • Keeping Fat Yes, fruit juice raises blood sugar quickly even when it is fresh-pressed. Whole fruit contains fibre. Fibre acts like a net, slowing down how fast the sugar enters your bloodstream. When you juice a fruit, you rip out the net. In a small Lancet study, apple juice called for more insulin than whole apples with the same sugar and was followed by a dip in blood sugar ([Haber et al., 1977](https://pubmed.ncbi.nlm.nih.gov/71495/)). ## 3. Is whole grain bread really better for blood sugar? 7/10 • Keeping Fat Only slightly: whole grain is better than white bread, but barely. It is still a heavily processed carbohydrate that turns into blood sugar within minutes of digestion, sitting firmly in the high range on the [glycemic index](https://realfoods.app/what-is-the-glycemic-index). Eating "healthy" whole-wheat toast every morning is a fast-digesting carbohydrate start to the day, not the protective swap most people assume. ## 4. Is granola bad for blood sugar? 8/10 • Keeping Fat Most commercial granola is: it is toasted oats bound with honey or syrup and dried fruit, which makes it mostly fast-digesting starch and sugar, and RealFoods scores it 8 out of 10. Often marketed with pictures of athletes and mountains, commercial granola is essentially broken down cake. It's toasted in honey, agave, or syrups, mixed with dried fruit (concentrated sugar), and delivers a heavy carbohydrate load that can set up a mid-morning hunger crash. Yogurt, toast, and granola all show up at breakfast, so start with the [high insulin breakfast foods to swap](https://realfoods.app/low-insulin-breakfast-foods). ## 5. Flavoured Oat Milk 7/10 • Keeping Fat Oats are starches. When you blend them into milk, you're drinking liquefied starch. Many commercial brands add sugar or use a chemical process to break down the oats into simple maltose sugars. An iced oat latte is often a disguised dessert. Ready to stop guessing what to eat? ![Download on the App Store](https://realfoods.app/download_appstore.png) ## 6. Protein Bars and "Healthy" Snack Bars 8/10 • Keeping Fat Check the ingredients. While they boast "20g of protein" on the front, the back often reveals 25g of carbohydrates tied together with syrups, artificial sweeteners, and dates. That much fast-digesting carbohydrate can raise blood sugar and insulin quickly, even with the protein alongside it. ## 7. Green Smoothies (Pre-Packaged) 7/10 • Keeping Fat That vibrant green hue might come from spinach, but the taste comes from apple chunks, bananas, and sometimes pure fruit extracts. The bigger issue is how much fruit and juice fits in one cup, often more than you would eat whole in one sitting. Blending itself matters less than people think: in one trial, blended mango did not raise blood sugar more than whole mango ([Redfern et al., 2017](https://pubmed.ncbi.nlm.nih.gov/28991222/)). ## 8. "Light" Salad Dressings 6/10 • Fat-Burning Paused Similar to yogurt, when the fat is stripped out of dressing, it separates quickly and tastes acidic. Food companies add thickeners and sugar to restore the texture. Ironically, full-fat olive oil dressings help you absorb the nutrients from the salad and are far less likely to push insulin up. ## 9. Rice Cakes 7/10 • Keeping Fat A staple of the 1990s low-fat craze. They are essentially puffed starch with zero fibre or protein to slow down digestion. Eating rice cakes can produce a quick rise in blood sugar, and for some people a hunger crash not long after. ## 10. Sports Drinks 9/10 • Keeping Fat Unless you are running a marathon or completing an intense 90-minute training session, you do not need to restock your glycogen stores with a sports drink. Drinking these casually delivers flavoured liquid sugar directly into your bloodstream. ## The Common Thread Foods marketed as "healthy" are often low in fat and high in sugar. In a small [nine-day trial in 43 children with obesity](https://pubmed.ncbi.nlm.nih.gov/26499447/) (Lustig et al., Obesity 2016), cutting dietary sugar from 28% to 10% of intake and replacing it with starch, at the same calories, improved blood pressure, cholesterol, blood sugar tolerance and insulin levels. The result can be a food that looks light on the label but still pushes blood sugar and insulin up. The fix is not a longer banned list. It is learning [what real food actually means](https://realfoods.app/real-food-weight-loss): ingredients you can recognize, not formulations built to look healthy. If you want the full food-by-food pattern, start with the [insulin resistance food guide](https://realfoods.app/insulin-resistance-diet). Knowing the [Weight Impact Score](https://realfoods.app/how-weight-impact-score-works) of a food before you eat it gives you an estimate before you eat, so you can choose a gentler option when you want to. ## Common questions ### What foods cause weight gain? Sugary drinks, fast-digesting starches such as potatoes and potato chips, and ultra-processed snacks are among the foods most strongly linked to weight gain in large studies. In a study of 120,877 U.S. adults followed for up to 20 years ([Mozaffarian et al., NEJM, 2011](https://pubmed.ncbi.nlm.nih.gov/21696306/)), potato chips, potatoes and sugar-sweetened drinks showed the strongest links to weight gain over four years, while vegetables, whole grains, fruit, nuts and yogurt were linked to less. In an NIH inpatient trial of 20 adults ([Hall et al., Cell Metabolism, 2019](https://pubmed.ncbi.nlm.nih.gov/31105044/)), people eating ultra-processed meals ate substantially more and gained about 0.9 kg over two weeks. ### What 'healthy' food is actually the worst for weight loss? Sports drinks (9/10) top this list, followed by flavoured low-fat yogurt, granola, and protein bars (all 8/10). All deliver liquid or fast-absorbing sugar with little fibre to slow absorption, which tends to produce a steep estimated insulin response despite calorie-light branding. ### Is whole wheat bread healthier than white bread? Marginally. Whole-wheat bread retains some fibre but is still heavily milled, so sugar absorption is rapid, and it typically sits in the same high range as white bread on the glycaemic index. It is a small step up, not the protective swap most people assume. Want to know why some people can eat pasta without gaining weight, but you seemingly can't? Read why [you're not losing weight eating healthy](https://realfoods.app/why-not-losing-weight-eating-healthy), or explore the [problem with calorie counting](https://realfoods.app/problem-with-calorie-counting). > **Medical disclaimer:** This article is for informational and educational purposes only. It is not medical advice and is not a substitute for diagnosis, treatment, or guidance from a licensed clinician. The Weight Impact Score is not a medical device and should not be used to diagnose, treat, cure, or prevent any disease. Always consult your physician or qualified health provider before changing your diet, especially if you have a medical condition, are taking medication, are pregnant, or are managing diabetes. Individual results vary. [Read the full disclaimer](https://realfoods.app/medical-disclaimer). > ![Dino Pohilj](https://realfoods.app/dino-pohilj-112.webp) > > Written by > > [Dino Pohilj](https://realfoods.app/authors/dino-pohilj) > > Founder, RealFoods > > Updated and reviewed October 6, 2026 Keep reading More on this thread. [Weight Loss Without Calorie Counting](https://realfoods.app/how-to-lose-weight-without-counting-calories) A practical four-step guide: protein, healthy fats and fibre at meals, a score per plate, and an optional overnight gap. [Weight Loss Without Constant Hunger](https://realfoods.app/lose-weight-without-hunger) The science of satiety: how protein, healthy fats and fibre help you stay fuller between meals.