FDA has not established a regulatory definition for "keto," "ketogenic," "keto-friendly," "low carb," or "net carbs." Unlike "low sodium" (≤140mg per serving), "high protein" (≥20% DV), or "sugar free" (<0.5g), these terms have no established regulatory thresholds in 21 CFR Part 101.
That absence of definition doesn't mean the claims are unrestricted. It means they're evaluated under different regulatory frameworks — general misbranding standards, FTC substantiation requirements, and consumer protection law — that can be harder to navigate precisely because the thresholds aren't spelled out.
"Low Carb" Has No FDA Definition
"Low carb" is not a defined nutrient content claim under FDA regulations. There is no CFR section that specifies what "low carb" means quantitatively, the way "low fat" (≤3g per serving) and "low sodium" (≤140mg per serving) are defined.
This creates a compliance question: is "low carb" a regulated claim or a general marketing term?
FDA's position, expressed in various guidance documents and warning letters, is that terms implying a specific nutrient level — even without a defined threshold — may be evaluated as implied nutrient content claims under 21 CFR 101.13. If consumers interpret "low carb" as meaning the product has a meaningfully low carbohydrate content, FDA can evaluate whether the product actually has a low carbohydrate content relative to comparable products.
In practice, FDA has not issued large numbers of warning letters specifically targeting "low carb" claims. But FTC has been more active — evaluating "low carb" claims against its substantiation standard and looking at whether the characterization is truthful and not misleading.
The risk isn't primarily regulatory enforcement. It's consumer protection litigation. Class action lawsuits against food brands for misleading "low carb" claims have cited both FDA misbranding standards and state consumer protection laws. When "low carb" appears on a product with 30g of total carbohydrates per serving alongside a category average of 35g, the argument that the claim is materially misleading has traction.
"Keto-Friendly" and "Keto-Certified"
"Keto-friendly" is similarly undefined by FDA. Third-party organizations — The Paleo Foundation (which offers a Keto Certified program), the Clean Keto Certification, and others — have created private certification standards for keto claims. These programs generally require total net carbs below a specified threshold (often ≤5g net carbs per serving) and may exclude certain sweeteners or additives.
Displaying a "Keto Certified" seal from a third-party program is permissible, but brands should understand what the certification program requires and whether those requirements align with how the product is actually formulated and marketed. A seal from a third-party certifier doesn't insulate a brand from FDA or FTC scrutiny if the underlying claims are misleading.
"Keto-friendly" without a certification program behind it is a general marketing term evaluated against the truthfulness and substantiation standards that apply to all advertising. If a product with 20g net carbs per serving is labeled "keto-friendly," and a ketogenic diet is generally understood to require <50g total carbs per day, a consumer eating three servings daily would consume 60g net carbs from that product alone — which may make the "keto-friendly" claim misleading in context.
"Net Carbs": The Label Compliance Problem
"Net carbs" — calculated as total carbohydrates minus dietary fiber and sugar alcohols — is not an FDA-recognized measurement for nutrition labeling purposes. It does not appear on the Nutrition Facts panel. FDA's required declaration is total carbohydrate, with dietary fiber and sugars (including added sugars) listed as sub-components.
Using "net carbs" on a label creates several compliance issues:
It cannot replace the required Nutrition Facts panel data. "Net carbs" appearing anywhere on the label must be clearly supplemental to the required total carbohydrate declaration on the Nutrition Facts panel, not a substitute for it. A label that emphasizes "only 3g net carbs" in large type while burying the required "total carbohydrate 22g" in the Nutrition Facts panel creates a misleading impression.
The calculation may be inaccurate. Not all dietary fiber reduces glycemic response, and not all sugar alcohols are fully absorbed. Erythritol has minimal caloric and glycemic impact; maltitol has significant glycemic impact and is not interchangeable with erythritol for carb subtraction purposes. A "net carbs" calculation that subtracts all sugar alcohols equally may overstate how keto-compatible the product is.
It may constitute a misleading implied claim. If "net carbs" is presented prominently and consumers reasonably interpret it as the carbohydrate count that matters for metabolic purposes, and if that interpretation is misleading for some sugar alcohols, FDA and FTC can evaluate the claim under general misbranding and substantiation standards.
Disease Claims Hidden in Keto Marketing
Keto and low-carb marketing frequently crosses into disease claim territory, especially when products are marketed for weight loss, metabolic health, or diabetes management.
Weight loss claims: A specific weight loss claim — "lose 10 pounds in 30 days on keto" — is a drug claim if it involves treating or preventing obesity as a disease. FTC's substantiation standard for weight loss claims is among the most stringent it applies: the "two RCT" standard means two well-designed, double-blinded, placebo-controlled human trials supporting the specific claim. Unsubstantiated weight loss claims are a primary target of FTC enforcement.
Blood sugar and diabetes claims: "Supports healthy blood sugar on a keto diet" may be a permissible structure/function claim. "Helps manage type 2 diabetes" is a disease claim. "Keto-friendly for diabetics" — implying suitability for diabetes management — creates disease claim implications that require careful review.
Cardiovascular claims: "Heart-healthy keto" paired with specific cardiovascular benefit claims — "reduces cholesterol," "lowers heart disease risk" — are disease claims. "Fits a heart-healthy lifestyle" is more evaluable but still carries risk depending on the product's actual saturated fat and sodium content.
The Interaction with Nutrition Facts Panel Requirements
Keto-positioned products often have unusual macronutrient profiles — high fat, moderate protein, very low carbohydrate — that create specific Nutrition Facts panel compliance considerations:
Fat calories: A product that derives more than 50% of its calories from fat must use the fat-based threshold for "light" claims (50% fat reduction vs. reference food), not the calorie-based threshold. Many keto products have high fat content that affects nutrient content claim eligibility.
Saturated fat disclosures: High saturated fat levels require the "not a low saturated fat food" or equivalent disclosure with certain claims. A "keto" product with 15g of saturated fat per serving that also carries a "healthy" claim fails the saturated fat threshold for "healthy" under the 2025 updated definition.
Calorie density: High-fat keto products are frequently calorie-dense. A 1 oz serving of a keto fat bomb may contain 200 calories. If the declared serving size is smaller than the RACC for the product category, FDA evaluates whether the serving size was manipulated to make calorie claims appear more favorable.
What Brands Should Do
Keto and low-carb claims are commercially valuable and legally permissible — with appropriate care. The practical compliance approach:
Use quantitative statements rather than undefined terms where possible: "8g total carbs per serving" is more defensible than "low carb"
Disclose total carbohydrates prominently in the Nutrition Facts panel; "net carbs" may supplement but cannot replace
Review all associated marketing claims — especially weight loss, blood sugar, and metabolic health claims — against FTC's substantiation standard
If using third-party keto certification, ensure the product genuinely meets the certifier's standards across all production runs
Undefined Claims Carry Defined Risks
The absence of a regulatory definition for "keto" doesn't mean keto claims are unregulated — it means they're evaluated under broader misbranding and FTC substantiation standards that are less predictable than defined threshold claims. Understanding that risk landscape is the starting point for building keto marketing that holds up.
Truli's AI compliance platform evaluates keto and low-carb claims against FDA misbranding standards and FTC substantiation requirements — flagging disease claim implications, verifying that "net carbs" language is supplemental to required Nutrition Facts panel data, and checking high-fat formulations against nutrient content claim eligibility thresholds. Book a demo to see how Truli handles claims compliance for keto and low-carb brands.
